| Abstract [eng] |
CRISPR-Cas systems – prokaryotic acquired immunity that provides rapid and robust adaptation to the rapidly evolving mobile genetic elements (MGEs). Several classes of MGE not only contributed to the origin and evolution of CRISPR–Cas, but also, conversely, CRISPR–Cas systems and their components were recruited by various MGEs. Viruses are considered to be unique among other MGEs, with CRISPR-Cas systems and their components that remain largely uncharacterized. In this study, bioinformatics analysis was performed in order to find and characterize CRISPR-Cas systems proteins homologs in viruses. Using profile-sequence (HMMER) and profile-profile (HH-suite) comparison searches, protein sequences encoded by 362 446 viruses were examined, of which 1 010 of the CRISPR-Cas systems proteins homologs were found. Viruses have been observed to incorporate Cas proteins into their genomes, mainly related to the adaptation and interference functional modules of the CRISPR-Cas systems. After grouping and analyzing the found sequences of CRISPR-Cas protein homologs, for the first time in this work the group of Csm3 proteins was characterized in viruses, possibly protecting the virus from the mechanism of host CRISPR-Cas systems. New groups of Cas5, Cas6 and Cas7 proteins have also been found, which require more detailed analysis to be described. Also, previously identified groups of Cas2, Cas3, Cas4, and Cas12/14 proteins have been identified in viruses, that are likely to be adapted to perform different viral functions, and the latter group is likely to act either as transposase or as part of the viral CRISPR-Cas complex. |
