Biology subjects

Lapsley, C.

Publications and source records attributed to Lapsley, C..

17 recordsLinked to original sources

bioRxiv2026

Restricted expression site use and extreme genome diversification drives trypanosome antigenic variation in chronic bovine infections

Trypanosoma brucei exploits an extreme form of antigenic variation to escape the mammalian immune response. This involves the progressive expression of antigenically distinct variant surface glycoproteins (VSGs) on the surface of individual parasites in the population, generating waves of parasitaemia that are successively cleared by host antibodies. Current paradigms were established using in vitro studies and acute rodent infections characterized by high parasitaemia, but natural livestock infections are characterized by low parasitaemia and chronicity. Here, we analysed the infection dynamics of isogenic parasites in mice and cattle in blood during early and chronic infections, quantitating VSG expression diversity within and between hosts, antigen type persistence in vivo and their timing of appearance. This revealed enhanced antigenic diversity in cattle but with a surprisingly reproducible temporal expression hierarchy of related VSGs between independent chronic infections. Analyses demonstrated the unexpected dominance of a single telomeric VSG expression site irrespective of host species and time of infection. Detailed prediction of mosaic VSG assembly reveals exceptional parasite genome diversification within infections involving extensive macro and micro-homology-based recombination to evolve the antigen repertoire. This diversity was restricted but not eliminated in homologous recombination mutants, which could nonetheless sustain chronic infections in mice. These data provide the first comprehensive insight into trypanosome antigenic variation in the clinically-relevant host.

microbiology↗

bioRxiv2026

Trypanosoma congolense Variant Surface Glycoprotein gene expression occurs in the absence of monoallelic transcription control

Antigenic variation is a very widespread process for pathogen evasion of mammalian adaptive immunity, involving the continuous change of exposed antigens. In many single-celled pathogens, antigen expression during antigenic variation is monoallelic: just a single gene from a large family is expressed in one cell at a time. In African trypanosomes, antigenic variation relies on expression of Variant Surface Glycoprotein (VSG), and in Trypanosoma brucei there is detailed understanding of the machinery that dictates that only one of approximately 15 VSG expression sites is actively transcribed at a time. In the closely related African trypanosome, T. congolense, which remains a significant blight on agriculture productivity in sub-Sharan Africa, we have no such understanding of VSG gene expression control or dynamics. Here, we have investigated the mechanics of antigenic variation in T. congolense, first examining the patterns of VSG expression at the transcript and protein level in small parasite populations in vitro. Surprisingly, this analysis revealed much greater VSG diversity than seen in T. brucei, with such expression diversity unaltered in mutants that impair homologous recombination. Using single cell transcriptomics, we explain this diversity, since we find no evidence for monoallelic transcription of T. congolense VSGs, but show instead that each parasite can dynamically express up to [~]40 different VSGs in a single cell both in vitro and in vivo. VSG co-expression occurs from VSG genes distributed across the genome, indicating the lack of a dedicated locus for VSG transcription. Thus, comparing two trypanosome species that rely on the same class of surface antigen for immune evasion has revealed highly distinct mechanisms for controlling antigen gene expression, challenging the assumed common operation of antigenic variation across African trypanosome species.

microbiology↗

bioRxiv2026

De novo assembly of the Trypanosoma congolense genome reveals an organisation influenced by antigenic variation but distinct from Trypanosoma brucei

Antigenic variation is a widespread process for pathogen evasion of mammalian adaptive immunity, involving the continuous change in exposed antigens. In African trypanosomes, antigenic variation involves changes in the expression of Variant Surface Glycoprotein (VSG). Understanding of VSG expression control and change amongst African trypanosomes is most advanced in Trypanosoma brucei. In the important animal trypanosome, Trypanosoma congolense, incomplete assembly of the genome has held back understanding of the mechanics of antigenic variation. Here, we have used long-read DNA sequencing and Hi-C DNA interaction analysis to provide a telomere-telomere assembly of the T. congolense genome. This assembly reveals a genome comprising 12 diploid chromosomes, one tetraploid chromosome, and more than 100 small chromosomes. Within this new assembly, we reveal several features of VSG organisation and expression that differ from T. brucei. The majority of the T. congolense VSG archive, estimated at [~]1500 genes, localises to subtelomeres in 12 of the 13 large chromosomes, but these loci are notably smaller than are found in T. brucei. Furthermore, transcriptome analysis reveals expression of VSGs across the T. congolense subtelomeres, which are not separated within the nucleus from non-VSG chromosome regions, indicating that there is no dedicated VSG expression site. Strikingly, one chromosome contains approximately 40% of the VSG archive and is largely transcriptionally silent, potentially acting as the major reservoir of new VSG variants. Finally, we show that VSG expression can be detected from multiple small chromosomes. In summary, the new genome assembly provides a platform for understanding a potentially unusual operation of VSG expression and switching in T. congolense.

microbiology↗

bioRxiv2026

Reduced levels of inositol hexakisphosphate kinase (IP6K) impair life-cycle transitions and the intracellular development of Trypanosoma cruzi within human cardiomyocytes

Trypanosoma cruzi is the etiological agent of Chagas disease. During its life cycle, T. cruzi undergoes several key differentiation processes that are essential for its survival. The precise mechanisms that regulate these processes remain elusive, and any interference in this cycle would represent a breakthrough in the development of effective therapy against Chagas disease. Here, after depleting a single IP6K allele of T. cruzi, we observed that key differentiation processes (metacyclogenesis, amastigogenesis and trypomastigogenesis) were profoundly impaired. Epimastigote forms of IP6K-deficient T. cruzi exhibited morphological alterations and reduced metacyclogenesis. IP6K-deficient metacyclic forms had reduced infective potential in human cardiomyocytes. IP6K-deficient amastigote forms showed impaired ability to transform into trypomastigotes, with most of the population egressing from human cardiomyocytes without completing trypomastigogenesis. Together, our results suggest that IP6K is critical to sustain the T. cruzi life cycle. Since disruption of both IP6K alleles was lethal and the primary structure of IP6K shares only [~]25% similarity with its human homolog, this kinase emerges as a promising target for drug development against Chagas disease. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=153 HEIGHT=200 SRC="FIGDIR/small/700787v2_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@1cb37f0org.highwire.dtl.DTLVardef@c59fb8org.highwire.dtl.DTLVardef@791cb7org.highwire.dtl.DTLVardef@14c68fd_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2024

Nuclear DNA replication in Leishmania major relies on a single constitutive origin per chromosome supplemented by thousands of stochastic initiation events

Understanding genome duplication requires characterisation of the locations where DNA replication initiates, termed origins. Genome-wide mapping of DNA replication origins has mainly been derived from population-based techniques, with only a few studies examining origin location and usage at the single-cell or single-molecule level. Leishmania are protozoan parasites where the first attempt to map DNA replication suggested the unprecedented use, for a eukaryote, of just a single origin per chromosome, while a subsequent approach suggested around 200-fold more origins. To reconcile these data and understand DNA replication dynamics in Leishmania major, we have applied DNAscent, a deep learning assay that uses long-read Nanopore sequencing to detect patterns of BrdU incorporation in individual DNA molecules, allowing the description of DNA replication fork movement and prediction of initiation and termination sites across the parasite genome. Our findings confirm the pre-eminence of a single locus of DNA replication initiation in each chromosome and reveal that this locus alone is constitutively activated in S-phase, with bidirectional forks emerging from discrete sites at the ends of multigene transcription units. DNAscent also reveals a much larger number of DNA replication initiation events that have not been detected in any previous mapping and are used stochastically, but whose abundance is greater as chromosome size increases. We show that each of these stochastic initiation sites localise to regions with high AT content, increased G-quadruplex levels and lower chromatin occupancy. In addition, we find markedly increased stochastic DNA replication initiation at sites with lower levels of nascent RNA transcripts. Finally, we show that all DNA replication initiation events result in mutagenesis. This work reveals a novel, bimodal strategy for DNA replication programming in Leishmania that drives genome transmission, replication timing and variation.

microbiology↗

bioRxiv2024

Genome-wide mapping of RPA1 and RAD9 reveals the management of polycistronic transcription, replication initiation, and responses to replication stress in Leishmania

When exposed single-stranded DNA accumulates at stalled or collapsed replication forks, the replication stress response is triggered to prevent genome instability. Leishmania are parasitic eukaryotes where gene expression is universally polycistronic and whose plastic genomes facilitate rapid adaptations in response to stress, with evidence implicating intrinsic replication stress as a source. Little is known about the Leishmania replication stress response. In this study, we reveal the global dynamics of the replication stress response in L. major promastigotes by performing ChIP-seq on three key replication stress response proteins, {gamma}H2A, RPA1 and RAD9, in the absence and presence of replication stress. We show that common hotspots of replication stress correlate with DNA replication initiation and transcription termination in Leishmania. When DNA replication is stalled, replication stress response factors accumulate at early S-phase origins, with a signal pattern reminiscent of bidirectional replication fork progression. Under conditions of chronic replication stress, increased accumulation of replication stress response factors emerges at wider sites of transcription initiation, suggesting Leishmania may possess compensatory strategies to limit the effects of replication stress and ensure DNA replication can complete under these conditions. In contrast, chronic replication stress enhances RSR factor accumulation at transcription termination sites, highlighting these regions as key replication stress hotspots in Leishmania. Lastly, variations in RPA dynamics in ATR-deficient cells uncover crucial roles of this protein kinase in managing polycistronic transcription and DNA replication, particularly under replication stress, in Leishmania. SummaryStrict controls operate to precisely copy an organisms DNA. However, cells need ways to rapidly adapt and respond to stimuli. In some cases, these beneficial adaptations come from problems during replication. Leishmania parasites cause serious neglected infections in humans and animals across the worlds tropics and sub-tropics. Remarkably, recent evidence suggests that Leishmania DNA experiences enhanced stress during replication that can drive its ability to rapidly adapt in response to stress. How Leishmania respond to DNA replication stress is still poorly understood. Here, using a genome-wide approach to map the locations of key proteins that manage DNA replication stress and maintain genome integrity, we show hotspots of DNA replication stress coincide with start sites of DNA replication and regions of transcription termination.

molecular biology↗

bioRxiv2024

Nanopore sequencing reveals that DNA replication compartmentalisation dictates genome stability and instability in Trypanosoma brucei

The genome of Trypanosoma brucei is structurally complex. Eleven megabase-sized chromosomes each comprise a transcribed core flanked by silent subtelomeres, housing thousands of Variant Surface Glycoprotein (VSG) genes. Additionally, silent VSGs are also found on hundreds of sub-megabase chromosomes that harbour 177 bp repeats of unknown function, and multiple VSG transcription sites localise to the telomeres of both chromosome types. DNA replication dynamics have been described in the megabase chromosome cores but not in the subtelomeres or sub-megabase chromosomes, and targeted early replication of the single active VSG transcription site is unexplained. Here, using Nanopore assembly, we mapped DNA replication across this compartmentalised genome. We show that subtelomeres display a paucity of replication initiation events relative to the core, correlating with increased instability in the silent VSG archive. In addition, early replication of the active VSG transcription site is shown to originate from the telomere, likely causing targeted VSG recombination. Lastly, we demonstrate that the 177 bp repeats act as widespread, conserved DNA replication origins, explaining mitotic stability of the abundant small chromosomes and early DNA replication of megabase chromosome centromeres. Compartmentalized DNA replication dynamics therefore explains how T. brucei balances stable genome transmission with localised instability driving immune evasion.

microbiology↗

bioRxiv2024

R-loops acted on by RNase H1 are a determinant of chromosome length-associated DNA replication timing and genome stability in Leishmania

Genomes in eukaryotes normally undergo DNA replication in a choreographed temporal order, resulting in early and late replicating chromosome compartments. Leishmania, a human protozoan parasite, displays an unconventional DNA replication program in which the timing of DNA replication completion is chromosome size-dependent: larger chromosomes complete replication later then smaller ones. Here we show that both R-loops and RNase H1, a ribonuclease that resolves RNA-DNA hybrids, accumulate in Leishmania major chromosomes in a pattern that reflects their replication timing. Furthermore, we demonstrate that such differential organisation of R-loops, RNase H1 and DNA replication timing across the parasites chromosomes correlates with size-dependent differences in chromatin accessibility, G quadruplex distribution and sequence content. Using conditional gene excision, we show that loss of RNase H1 leads to transient growth perturbation and permanently abrogates the differences in DNA replication timing across chromosomes, as well as altering levels of aneuploidy and increasing chromosome instability in a size-dependent manner. This work provides a link between R-loop homeostasis and DNA replication timing in a eukaryotic parasite and demonstrates that orchestration of DNA replication dictates levels of genome plasticity in Leishmania.

microbiology↗

bioRxiv2024

Genomic diversity of novel strains of mammalian gut microbiome derived Clostridium XIVa strains is driven by mobile genetic element acquisition

Despite advances in sequencing technologies that enable a greater understanding of mammalian gut microbiome composition, our ability to determine a role for individual strains is hampered by our inability to isolate, culture and study such microbes. Here we describe highly unusual Clostridium XIVa group strains isolated from the murine gut. Genome sequencing indicates that these strains, Clostridium symbiosum LM19B and LM19R and Clostridium clostridioforme LM41 and LM42, have significantly larger genomes than most closely related strains. Genomic evidence indicates that the isolated LM41 and LM42 strains diverge from most other Clostridium XIVa strains and supports reassignment of these groups at genus-level. We attribute increased C. clostridioforme LM41 and LM42 genome size to acquisition of mobile genetic elements including dozens of prophages, integrative elements, putative group II introns and numerous transposons including 29 identical copies of the IS66 transposase, and a very large 192 Kb plasmid. antiSmash analysis determines a greater number of biosynthetic gene clusters within LM41 and LM42 than in related strains, encoding a diverse array of potential novel antimicrobial compounds. Together these strains highlight the potential untapped microbial diversity that remains to be discovered within the gut microbiome and indicate that, despite our ability to get a top down view of microbial diversity, we remain significantly blinded to microbe capabilities at the strain level.

microbiology↗

bioRxiv2023

RAD51-mediated R-loop formation acts to repair transcription-associated DNA breaks driving antigenic variation in Trypanosoma brucei

RNA-DNA hybrids are epigenetic features of all genomes that intersect with many processes, including transcription, telomere homeostasis and centromere function. Increasing evidence suggests RNA-DNA hybrids can provide two conflicting roles in the maintenance and transmission of genomes: they can be the triggers of DNA damage, leading to genome change, or can aid the DNA repair processes needed to respond to DNA lesions. Evasion of host immunity by African trypanosomes, such as Trypanosoma brucei, relies on targeted recombination of silent Variant Surface Glycoprotein (VSG) genes into a specialised telomeric locus that directs transcription of just one VSG from thousands. How such VSG recombination is targeted and initiated is unclear. Here, we show that a key enzyme of T. brucei homologous recombination, RAD51, interacts with RNA-DNA hybrids. In addition, we show that RNA-DNA hybrids display a genome- wide co-localisation with DNA breaks, and that this relationship is impaired by mutation of RAD51. Finally, we show that RAD51 acts to repair highly abundant, localised DNA breaks at the single transcribed VSG, and that mutation of RAD51 alters RNA-DNA hybrid abundance both around the transcribed VSG and across the silent VSG archive. This work reveals a widespread, generalised role for RNA-DNA hybrids in directing RAD51 activity during recombination and uncovers a specialised application of this interplay during targeted DNA break repair needed for the critical T. brucei immune evasion reaction of antigenic variation.

microbiology↗

bioRxiv2021

Widespread roles of Trypanosoma brucei ATR in nuclear genome function and transmission are linked to R-loops

Inheritance of aberrant chromosomes can compromise genome integrity and affect cellular fitness. In eukaryotes, surveillance pathways and cell cycle checkpoints monitor for aberrant DNA transmission and the ATR kinase, a regulator of the DNA damage response, plays a pivotal role. Prior work revealed that ATR acts during antigenic variation in Trypanosoma brucei mammal-infective life cycle forms and that its loss is lethal, but how widely ATR operates in genome maintenance is largely unknown. Here, we show that after prolonged ATR depletion by RNAi T. brucei continues to synthesise DNA and enters new rounds of cell division, despite increased genome damage. Furthermore, we detect defective chromosome segregation, micronuclei formation and disruption of the nuclear architecture. RNA-seq revealed that loss of ATR affects the expression of nearly half the genes in the genome, including both RNA Polymerase I and II transcription. Using ChIP-seq of yH2A and DRIP-seq, we reveal overlapping signals for genome damage and R-loops after ATR depletion in all intergenic regions. In addition, we report reduced R-loop levels and accumulation of yH2A signal within centromeres. Together, our data indicates widespread roles of ATR in T. brucei, including differing roles in R-loop homeostasis during multigene transcription and in chromosome segregation.

cell biology↗

bioRxiv2019

Conditional knockout of RAD51-related genes in Leishmania major reveals a critical role for homologous recombination during genome replication

Homologous recombination (HR) has an intimate relationship with genome replication, both during repair of DNA lesions that might prevent DNA synthesis and in tackling stalls to the replication fork. Recent studies led us to ask if HR might have a more central role in replicating the genome of Leishmania, a eukaryotic parasite. Conflicting evidence has emerged regarding whether or not HR genes are essential, and genome-wide mapping has provided evidence for an unorthodox organisation of DNA replication initiation sites, termed origins. To answer this question, we have employed a combined CRISPR/Cas9 and DiCre approach to rapidly generate and assess the effect of conditional ablation of RAD51 and three RAD51-related proteins in Leishmania major. Using this approach, we demonstrate that loss of any of these HR factors is not immediately lethal, but in each case growth slows with time and leads to DNA damage, accumulation of cells with aberrant DNA content, and genome-wide mutation. Despite these similarities, we show that only loss of RAD51 and RAD51-3 impairs DNA synthesis, and that the factors act in distinct ways. Finally, we reveal that loss of RAD51 has a profound effect on DNA replication, causing loss of initiation at the major origins and increased DNA synthesis at subtelomeres. Our work clarifies questions regarding the importance of HR to survival of Leishmania and reveals an unanticipated, central role for RAD51 in the programme of genome replication in a microbial eukaryote.

microbiology↗

bioRxiv2019

Genome duplication in Leishmania major relies on DNA replication outside S phase

Once every cell cycle, DNA replication takes place to allow cells to duplicate their genome and segregate the two resulting copies into offspring cells. In eukaryotes, the number of DNA replication initiation loci, termed origins, is proportional to chromosome size. However, previous studies have suggested that in Leishmania, a group of single-celled eukaryotic parasites, DNA replication starts from just a single origin per chromosome, which is predicted to be insufficient to secure complete genome duplication within S phase. Here, we show that the paucity of origins activated in early S phase is balanced by DNA synthesis activity outside S phase. Simultaneous recruitment of acetylated histone H3 (AcH3), modified base J and the kinetochore factor KKT1 is exclusively found at the origins used in early S phase, while subtelomeric DNA replication can only be linked to AcH3 and displays persistent activity through the cell cycle, including in G2/M and G1 phases. We also show that subtelomeric DNA replication, unlike replication from the previously mapped origins, is sensitive to hydroxyurea and dependent on subunits of the 9-1-1 complex. Our work indicates that Leishmania genome transmission relies on an unconventional DNA replication programme, which may have implications for genome stability in this important parasite.

microbiology↗

bioRxiv2019

Trypanosoma brucei ribonuclease H2A is an essential enzyme that resolves R-loops associated with transcription initiation and antigenic variation

In every cell ribonucleotides represent a threat to the stability and transmission of the DNA genome. Two types of Ribonuclease H (RNase H) tackle such ribonucleotides, either by excision when they form part of the DNA strand, or by hydrolysing RNA when it base-pairs with DNA, in structures termed R-loops. Loss of either RNase H is lethal in mammals, whereas yeast can prosper in the absence of both enzymes. Removal of RNase H1 is tolerated by the parasite Trypanosoma brucei but no work has examined the function of RNase H2. Here we show that loss of the catalytic subunit of T. brucei RNase H2 (TbRH2A) leads to growth and cell cycle arrest that is concomitant with accumulation of nuclear damage at sites of RNA polymerase (Pol) II transcription initiation, revealing a novel and critical role for RNase H2. In addition, differential gene expression of both RNA Pol I and II transcribed genes occurs after TbRH2A loss, including patterns that may relate to cytosolic DNA accumulation in humans with autoimmune disease. Finally, we show that TbRH2A loss causes R-loop and DNA damage accumulation in telomeric RNA Pol I transcription sites, leading to altered variant surface glycoprotein expression. Thus, we demonstrate a separation of function between the two nuclear T. brucei RNase H enzymes during RNA Pol II transcription, but overlap in function during RNA Pol I-mediated gene expression during host immune evasion.

microbiology↗

bioRxiv2018

The ATR kinase of Trypanosoma brucei links DNA damage signalling and monoallelic control of surface antigen gene expression during antigenic variation

To evade mammalian immunity, Trypanosoma brucei switches the variant surface glycoprotein (VSG) expressed on its surface. Key to this reaction are controls exerted to ensure only one of many subtelomeric multigene VSG expression sites are transcribed at a time. DNA repair activities have to date been implicated only in catalysis of VSG switching by recombination, not transcriptional control. However, how VSG switching is signalled to guide the appropriate reaction, or to integrate switching into parasite growth, is unknown. Here we show that loss of ATR, a DNA damage signalling protein kinase, is lethal and causes increased nuclear genome lesions. ATR depletion also causes expression of mixed VSGs on the cell surface, increased transcription of genes from silent expression sites, and altered localisation of RNA Polymerase I and VEX1, factors involved in VSG transcription. The work therefore reveals that VSG expression control is mediated by a nuclear DNA damage signalling factor.

molecular biology↗

bioRxiv2018

RibonucleaseH1-targeted R-loops in surface antigen gene expression sites can direct trypanosome immune evasion

Switching of the Variant Surface Glycoprotein (VSG) in Trypanosoma brucei provides a crucial host immune evasion strategy that is catalysed both by transcription and recombination reactions, each operating within specialised telomeric VSG expression sites (ES). VSG switching is likely triggered by events focused on the single actively transcribed ES, from a repertoire of around 15, but the nature of such events is unclear. Here we show that RNA-DNA hybrids, called R-loops, form preferentially within sequences termed the 70 bp repeats in the actively transcribed ES, but spread throughout the active and inactive ES in the absence of RNase H1, which degrades R-loops. Loss of RNase H1 also leads to increased levels of VSG coat switching and replication-associated genome damage, some of which accumulates within the active ES. This work indicates VSG ES architecture elicits R-loop formation, and that these RNA-DNA hybrids connect T. brucei immune evasion by transcription and recombination.\n\nAuthor summaryAll pathogens must survive eradication by the host immune response in order to continue infections and be passed on to a new host. Changes in the proteins expressed on the surface of the pathogen, or on the surface of the cells the pathogen infects, is a widely used strategy to escape immune elimination. Understanding how this survival strategy, termed antigenic variation, operates in any pathogen is critical, both to understand interaction between the pathogen and host and disease progression. A key event in antigenic variation is the initiation of the change in expression of the surface protein gene, though how this occurs has been detailed in very few pathogens. Here we examine how changes in expression of the surface coat of the African trypanosome, which causes sleeping sickness disease, are initiated. We reveal that specialised nucleic acid structures, termed R-loops, form around the expressed trypanosome surface protein gene and increase in abundance after mutation of an enzyme that removes them, leading to increased changes in the surface coat in trypanosome cells that are dividing. We therefore shed light on the earliest acting events in trypanosome antigenic variation.

microbiology↗

bioRxiv2018

Genome-wide mapping reveals conserved and diverged R-loop activities in the unusual genetic landscape of the African trypanosome genome

R-loops are stable RNA-DNA hybrids that have been implicated in transcription initiation and termination, as well as in telomere homeostasis, chromatin formation, and genome replication and instability. RNA Polymerase (Pol) II transcription in the protozoan parasite Trypanosoma brucei is highly unusual: virtually all genes are co-transcribed from multigene transcription units, with mRNAs generated by linked trans-splicing and polyadenylation, and transcription initiation sites display no conserved promoter motifs. Here, we describe the genome-wide distribution of R-loops in wild type mammal-infective T. brucei and in mutants lacking RNase H1, revealing both conserved and diverged functions. Conserved localisation was found at centromeres, rRNA genes and retrotransposon-associated genes. RNA Pol II transcription initiation sites also displayed R-loops, suggesting a broadly conserved role despite the lack of promoter conservation or transcription initiation regulation. However, the most abundant sites of R-loop enrichment were within the intergenic regions of the multigene transcription units, where the hybrids coincide with sites of polyadenylation and nucleosome-depletion. Thus, instead of functioning in transcription termination, most T. brucei R-loops act in a novel role, promoting RNA Pol II movement or mRNA processing. Finally, we show there is little evidence for correlation between R-loop localisation and mapped sites of DNA replication initiation.

genomics↗