Biology subjects

Lavrov, A.

Publications and source records attributed to Lavrov, A..

3 recordsLinked to original sources

bioRxiv2025

Translation of numerous upstream open reading frames rather than their products is essential for proliferation of human cells of distinct origin

Upstream open reading frames (uORFs) are a widespread class of translated regions (translons) occurring in 5' leaders of mRNAs and serving critical roles in post-transcriptional regulation. However, their specific biological activities in human cells remains to be fully elucidated. Here, we conducted a genome-wide CRISPR-Cas9 loss-of-function screen of 978 uORFs identified with ribosome profiling, across human cell lines of distinct origin (HAP1, A549 and HEK293T). A total of 155 uORFs were identified as being essential for cell proliferation. These uORFs showed a high cell-type specificity, with only a few being universally essential. Subsequent analysis has revealed that the primary reason underlying the uORF essentiality is not encoded micropeptides, but rather cis-regulatory mechanisms. Moreover, uORFs located within short 5' UTRs were disproportionately sensitive to frameshift-inducing indels, which frequently lead to the uORF extension and overlap with the coding region (CDS), resulting in translational repression. Finally, by intersecting regions of essential uORF with ClinVar and dbSNP datasets, we identified naturally occurring variants with the potential to disrupt their function and contribute to disease phenotypes. These findings highlight a pervasive and underappreciated layer of translational control in human cells and establish uORFs as critical cis-regulatory elements with potential relevance to human health.

molecular biology↗

bioRxiv2024

First draft genome assembly and characterization of sponge Halisarca dujardinii reveals key components of basement membrane and broad repertoire of aggregation factors

How features characteristic of multicellular animals emerged in evolution and how the body plan of particular taxa was shaped are hotspots of modern evolutionary biology. We can get closer to answering them by studying animals that occupy a basal position on the phylogenetic tree, such as sponges (Porifera). We sequenced the genome of the sponge Halisarca dujardinii using Oxford Nanopore and Illumina technologies and made an assembly of long reads, followed by polishing with short reads. The resulting assembly had a size of 176 Mb, matching the prediction from the k-mer distribution, and an N50 of about 785 Kb. By analyzing transposable elements in the genomes of H. dujardinii and a number of other sponges, we found that a significant portion of the genome (more than half for Demospongiae) is occupied by repeats, most of which are evolutionary young. RNA-seq data were used to predict about 14000 genes in the genome, several times less than in other Demospongiae. By analyzing ortholog groups unique to H. dujardinii among sponges and higher invertebrates, we found overrepresented genes related to the extracellular matrix. The extracellular matrix of H. dujardinii contains, among others, key basement membrane components such as laminin, nidogen, fibronectin, and collagen IV, for which phylogenetic analysis has confirmed that it belongs to this type of nonfibrillar collagen. In addition, we showed in H. dujardinii 14 aggregation factor genes responsible for cell recognition and adhesion. They are organized in a genomic cluster and have at least two types of domains: Calx-beta, responsible for calcium ion binding, and Wreath domain, unique for this type of molecules. Our obtained assembly and annotation will further expand the understanding of genome evolution at the emergence of animal multicellularity, and will serve as a tool to study the regulation of gene expression by modern methods.

genomics↗

bioRxiv2019

Variants in the degron of AFF3 cause a multi-system disorder with mesomelic dysplasia, horseshoe kidney and developmental and epileptic encephalopathy

The ALF transcription factor paralogs, AFF1, AFF2, AFF3 and AFF4, are components of the transcriptional super elongation complex that regulates expression of genes involved in neurogenesis and development. We describe a new autosomal dominant disorder associated with de novo missense variants in the degron of AFF3, a nine amino acid sequence important for its degradation. Consistent with a causative role of AFF3 variants, the mutated AFF3 proteins show reduced clearance. Ten affected individuals were identified, and present with a recognizable pattern of anomalies, which we named KINSSHIP syndrome (KI for horseshoe KIdney, NS for Nievergelt/Savarirayan type of mesomelic dysplasia, S for Seizures, H for Hypertrichosis, I for Intellectual disability and P for Pulmonary involvement), partially overlapping the AFF4 associated CHOPS syndrome. An eleventh individual with a microdeletion encompassing only the transactivation domain and degron motif of AFF3 exhibited overlapping clinical features. A zebrafish overexpression model that shows body axis anomalies provides further support for the pathological effect of increased amount of AFF3 protein.\n\nWhereas homozygous Aff3 knockout mice display skeletal anomalies, kidney defects, brain malformation and neurological anomalies, knock-in animals modeling the microdeletion and the missense variants identified in affected individuals presented with lower mesomelic limb deformities and early lethality, respectively.\n\nTranscriptome analyses as well as the partial phenotypic overlap of syndromes associated with AFF3 and AFF4 variants suggest that ALF transcription factors are not redundant in contrast to what was previously suggested

genetics↗