Biology subjects

Ryazansky, S.

Publications and source records attributed to Ryazansky, S..

2 recordsLinked to original sources

bioRxiv2018

The expanded universe of prokaryotic Argonaute proteins

The members of the ancient family of Argonaute (Ago) proteins are present in all domains of life. The common feature of Ago proteins is the ability to bind small nucleic acid guides and use them for sequence-specific recognition - and sometimes cleavage - of complementary targets. While eukaryotic Ago (eAgo) proteins are key players in RNA interference and related pathways, the properties and functions of these proteins in archaeal and bacterial species have just started to emerge. We undertook comprehensive exploration of prokaryotic Ago (pAgo) proteins in sequenced genomes and almost tripled the number of previously analyzed genes of this family. In comparison with eAgos, pAgos are highly diverse and have likely spread by horizontal gene transfer. Many pAgos contain divergent variants of the conserved domains involved in interactions with nucleic acids and in target cleavage, while having extra domains that are absent in eAgos, suggesting that they might have unusual specificities in the nucleic acid recognition and processing. Many pAgos, including catalytically inactive variants, are associated with putative nucleases, helicases and DNA binding proteins in the same gene or operon, suggesting that they are involved in DNA processing. The great diversity of pAgos revealed by our analysis opens new ways for exploration of their functions in host cells and their use as potential tools in genome editing.

genomics↗

bioRxiv2017

Key role of piRNAs in telomeric chromatin maintenance and telomere nuclear positioning in Drosophila germline

Telomeric small RNAs related to PIWI-interacting RNAs (piRNAs) were discovered in different species, however, their role in germline-specific telomere function remains poorly understood. Using a Drosophila model, we show that the piRNA pathway provides a strong germline-specific mechanism of telomere homeostasis. We show that telomeric retrotransposon arrays belong to a unique class of dual-strand piRNA clusters whose transcripts, required for telomere elongation, serve simultaneously as piRNA precursors and their only targets. However, the ability to produce piRNAs and bind Rhino - a germline-specific homolog of heterochromatic protein 1 (HP1) - varies along telomeres. Most likely, this heterogeneity is determined by the peculiarities of telomeric retrotransposons themselves. piRNAs play a pivotal role in the establishment and maintenance of telomeric and subtelomeric chromatin in the germline facilitating loading of HP1 and histone 3 lysine 9 trimethylation mark - highly conservative telomere components - at different telomeric regions. piRNA pathway disruption results in telomere dysfunction characterized by a loss of heterochromatic components and translocation of telomeres from the periphery to the nuclear interior but does not affect the telomere end capping.

genomics↗