Biology subjects

Seistrup, A.-S.

Publications and source records attributed to Seistrup, A.-S..

5 recordsLinked to original sources

bioRxiv2026

SLBP-independent control of maternal histone mRNA

Replication-dependent (RD) histones are crucial for packaging newly replicated DNA into chromatin, ensuring genome stability. In metazoans, the mRNA of RD histones is uniquely regulated through a conserved 3' stem-loop bound by stem-loop binding protein (SLBP). This allows cell cycle-coupled regulation of these important transcripts. However, oocytes must stabilise histone mRNAs independently of the cell cycle to ensure maternal loading to support the first embryonic divisions. Using Caenorhabditis elegans as a model system, we discovered an SLBP-independent mechanism that ensures RD histone transcript stability during oogenesis. This is mediated by the protein complex PETISCO, bound to the effector protein TOST-1, which directly binds the histone stem-loop region and maintains maternal histone mRNA levels during oogenesis and early embryogenesis. Loss of this mechanism disrupts histone homeostasis, leading to premature genome activation, mitotic defects, and embryonic lethality. Interestingly, the same complex, PETISCO, acts in piRNA biogenesis when bound to the effector PID-1, revealing an intriguing co-option of this histone mRNA homeostasis mechanism by the piRNA pathway. Our findings reveal a unique SLBP-independent mechanism of histone mRNA regulation, that served as a basis for the evolution of a novel piRNA biogenesis mechanism.

molecular biology↗

bioRxiv2025

Proteolytic Control of an Auto-inhibitory Intrinsically Disordered Region Governs Small RNA Selectivity in Argonaute Proteins

Argonaute proteins are central to small RNA-mediated gene regulation, yet the mechanisms controlling their activity remain incompletely understood. We elucidate a novel regulatory mechanism governing small RNA loading into the C. elegans Argonaute proteins WAGO-1 and WAGO-3. We show that N-terminal intrinsically disordered regions (N-IDRs) of these proteins do not affect subcellular localization but play critical roles in small RNA loading. We demonstrate that the N-IDR-processing protease DPF-3 facilitates small RNA loading in a catalysis-independent manner. Catalysis by DPF-3 and a second protease APP-1 is required, however, for activity. Deletion of these N-IDRs results in loading of aberrant small RNA species that trigger erroneous gene silencing. Supported by atomistic molecular dynamics simulations, we propose a model in which N-IDRs can simultaneously act as tuneable gatekeepers that auto-inhibit small RNA loading and as regulators of Argonaute stability, representing a previously unrecognized layer of regulation in Argonaute activity in small RNA pathways.

molecular biology↗

bioRxiv2025

Crosstalk between and developmental dynamics of C. elegans Argonaute proteins

Gene regulation via Argonaute-bound small RNAs is a broadly conserved mechanism, present in all domains of life. The nematode Caenorhabditis elegans expresses several worm-specific Argonautes (WAGOs), which interact with the small RNAs known as 22G-RNAs. These WAGOs have roles in gene regulation, transposon-defence as well as in viral control and experimentally induced RNA interference. Despite many studies, direct relationships between WAGO targeting, as defined by 22G RNA sequences, and mRNA abundance are not clear. Also, the effects of developmental stage and WAGO-interconnectivity have been under-studied thus far. We studied these aspects for two germline-expressed WAGO proteins, WAGO-1 and WAGO-3. We show that WAGO-1 mostly affects 22G-RNA expression in gravid adult worms, while WAGO-3 predominantly affects 22G-RNA expression in embryos. Furthermore, we detect a link between WAGO-3 and the maternal 26G-RNA pathway governed by the Argonaute protein ERGO-1, and between WAGO-1 and the paternal 26G-RNA pathway governed by the Argonautes ALG-3/4. We also demonstrate that, globally speaking, loss of WAGO-1 or WAGO-3 does not result in upregulation of their target mRNAs, as defined by 22G-RNA complementarity. Finally, metagene analysis of 22G-RNA profiles suggests loss of one WAGO protein leads to shifts in WAGO 22G-RNA binding. Overall, we conclude that WAGO-1 and WAGO-3 are developmentally dynamic, are embedded in distinct regulatory networks, and that potential silencing of individual mRNAs by these WAGO proteins is hard to assess by simple loss-of-function studies. SummaryRNA interference describes silencing of genes via small RNAs coupled to an Argonaute protein. C. elegans expresses a class of secondary small RNAs known as 22G-RNAs which are coupled to Argonautes known as WAGOs (worm-specific Argonautes). We have sequenced 22G-RNA and mRNA populations from deletion mutants of two such WAGOs, WAGO-1 and WAGO-3, to investigate Argonaute crosstalk and the relationship between 22G-RNA and mRNA levels. We found that WAGO-1 and WAGO-3 engage different, complementary pathways, and that target silencing cannot be deduced simply from 22G-RNA complementarity.

genetics↗

bioRxiv2023

Age- and caste-independent piRNAs in the germline and miRNA profiles linked to caste and fecundity in the ant Temnothorax rugatulus

Social insects are models for phenotypic plasticity: the generation of different phenotypes from the same genotype. Ant queens and workers differ not only in their morphology and behaviour, but also in their fecundity and lifespan, which is often several times higher in queens. However, the gene regulatory mechanisms underlying these differences are not yet well understood. Since ant queens can live and reproduce for more than two decades, they need to protect their germline from the activity of transposable elements (TEs). This protection may be redundant in short-lived, often sterile workers. We have analysed the expression of two protective classes of smallRNAs, microRNAs (miRNAs) and Piwi-interacting RNAs (piRNAs), in different tissues, castes, and age classes of the ant species Temnothorax rugatulus. We show that piRNAs are particularly active in the ovaries of queens. TEs are clear targets of the piRNAs in this ant species, and piRNA-specific sequence signatures in the ovaries of all queens regardless of age indicate that young and old queens have similarly active piRNA pathways. Interestingly, the reduced ovaries of the workers also showed the same level of piRNA activity. This was not only the case in young, fertile workers from queenless nests, but also in the presumably older foragers, which have almost completely regressed ovaries. These findings suggest that the germline in these ants is invariably protected by piRNA activity, irrespective of ovarian development. The brain and thorax of queens also contained piRNAs, but at lower levels, and the piRNA-specific ping-pong signatures were strongly reduced in these tissues. We also annotated and analysed miRNAs in different tissues. We confidently detected the expression of 304 miRNAs. Of these, 10 were enriched in the brain and three to the thorax, whereas 83 were specific to the ovaries. 105 miRNAs were found to be expressed in all three tissues. We also identified miRNAs whose expression potentially is related to ant caste, fecundity, and age, suggesting that caste-specific gene activity may be regulated in part by miRNAs. In contrast, our studies of piRNA activity indicate similar profiles across caste, fecundity and age groups, but strong tissue specificity with the highest piRNA mediated TE protection in the germline.

ecology↗

bioRxiv2020

A membrane-associated condensate drives paternal epigenetic inheritance in C. elegans

Transgenerational epigenetic inheritance (TEI) describes the transmission of gene-regulatory information across generations without altering DNA sequences, and allows priming of offspring towards transposable elements (TEs) and changing environmental conditions. One important mechanism that acts in TEI is based on small non-coding RNAs. Whereas factors for maternal inheritance of small RNAs have been identified, paternal inheritance is poorly understood, as much of the cellular content is extruded during spermatogenesis. We identify a phase separation-based mechanism, driven by the protein PEI-1, which is characterized by a BTB-BACK domain and an intrinsically disordered region (IDR). PEI-1 specifically secures the Argonaute protein WAGO-3 within maturing sperm in C. elegans. Localization of PEI granules in mature sperm is coupled, via S-palmitoylation, to myosin-driven transport of membranous organelles. pei-1-like genes are also found in human and often expressed in testis, suggesting that the here identified mechanism may be broadly conserved.

cell biology↗