013. Видання НаУКМА

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Browsing 013. Видання НаУКМА by Author "Antonyuk, Maksym"

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    Molecular strategies of viral replication and their impact on the evolution of genomes of cellular organisms
    (Національний університет "Києво-Могилянська академія", 2026) Hisem, Maksym; Antonyuk, Maksym
    The article explores the fundamental role of viruses as generators of genetic variability and driving force of macroevolutionary processes in the biosphere. Molecular biological strategies of virus replication are analyzed within the paradigm of the Baltimore classification, which considers the genome type as а determinant of transcriptional logic and adaptive potential of viral lineages. Attention is focused on enzymatic replication systems – RNA-dependent RNA polymerase (RdRp) and reverse transcriptase (RT), devoid of an error correction mechanism. It is proven that the high frequency of incorporation of noncomplementary nucleotides and structural variability due to template changes lead to the formation of quasispecies – highly dynamic populations of genetically related subvariants, which ensure evolutionary plasticity and survival of the virus under selective pressure. The molecular mechanisms of viral genome integration into host cell chromosomes as а basic pathway of horizontal gene transfer are outlined. Obligate integration of retroviruses mediated by viral integrases with co-optation of cellular proteins for chromatin navigation are considered, as well as the mechanisms of lysogeny of temperate bacteriophages, which determine the genetic plasticity of prokaryotes and their acquisition of new phenotypic traits (in particular, pathogenicity and stress resistance). The phenomenon of the formation of endogenous viral elements (EVE) because of ancient integrations into eukaryotic germline cells, which became а substrate for the emergence of new regulatory sequences, is described. Hypotheses of the origin of viruses are synthesized. The concept of polyphyletic origin is asserted, according to which different viral classes evolved independently from distinct predecessors (plasmids, retrotransposons) through horizontal gene transfer, gene loss, and recombination, which makes it impossible to identify а single common ancestor. The central aspect of the work is the analysis of the consequences of viral-cellular coevolution through the mechanism of molecular exaptation – co-optation of viral genes by host organisms to perform new biological functions. The molecular basis of the formation of morphophysiological structures and immune mechanisms based on integrated viral sequences is presented. Examples are detailed: fusogenic activity of retroviral syncytin proteins during placentation; the origin of the neuronal gene Arc, which provides intercellular communication and synaptic plasticity, from а retrotransposon; the transposon origin of RAGrecombinase enzymes responsible for somatic recombination of gene segments in the vertebrate adaptive immune system; the evolution of the CRISPR-Cas adaptive immune system of bacteria from casposons; the role of endogenous retroviruses in maintaining the pluripotency of embryonic stem cells (HERV-H) and the functioning of their LTR regions as transcriptional enhancers (MER41). It is argued that viruses are а critical architectural element in the formation of genomes and the evolutionary complexity of cellular biological systems.