Biology subjects

Homola, M.

Publications and source records attributed to Homola, M..

3 recordsLinked to original sources

bioRxiv2026

Emergence of histone-based chromatin complexity in Asgard archaea

The emergence of the eukaryotes coincided with the diversification of histone proteins and their post-translational modifications by enzymes that constitute the core of eukaryotic chromatin. Yet the evolutionary origins of this regulatory machinery are unknown. Here, we show that the key molecular components of histone-based chromatin regulation are present in the Asgard archaea, the closest prokaryotic relatives of eukaryotes. Asgard histones are abundant and have extended N-terminal tails rich in lysine residues that can be post-translationally modified, all of which are features shared with eukaryotic histones. In line with these findings, we identify enzymes from Asgard archaea that deposit or remove lysine acetylation on histone tails in vitro. Moreover, Asgard sirtuin deacetylases (SIR2 proteins) restore chromatin silencing in yeast, demonstrating the functional compatibility of Asgard enzymes with eukaryotic histone substrates. Our findings establish that the foundations of histone-based chromatin predate eukaryogenesis and place Asgard archaea as an evolutionary intermediate in the emergence of eukaryotic chromatin.

evolutionary biology↗

bioRxiv2026

Active virus-host system in a Lokiarchaeon culture

Asgard archaea are considered the closest prokaryotic relatives of eukaryotes and having a crucial role in eukaryogenesis. Only few organisms have been cultivated from this group and their viruses were previously described only through metagenomic reconstructions. Here, we report the first successful cultivation of an Asgard archaeal virus infecting a novel strain of Ca. Lokiarchaeum ossiferum B36. The 16 kbp integrated provirus is capable to excise and replicate independently leading to the formation of virus particles. Network analysis of shared protein clusters with other archaeal viruses places it in a new family, Fylgjaviridae. The host encodes a distinctive repertoire of antiviral defense systems, including Septu, Wadjet, and type II CBASS system, all different from the defense systems of the related strain Ca. L. ossiferum B35. Our cultures provide the first opportunity to study interactions of a virus-host system in Asgards and hold significant potential for developing genetic tools.

microbiology↗

bioRxiv2023

Structure and replication cycle of a virus infecting climate-modulating alga Emiliania huxleyi

The globally distributed marine alga Emiliania huxleyi produces reflective calcite disks (coccoliths) that increase the albedo of ocean water and thus reduce the heat absorption in the ocean, which cools the Earths climate. The population density of E. huxleyi is restricted by nucleocytoplasmic large DNA viruses, including E. huxleyi virus 201 (EhV-201). Despite the impact of E. huxleyi viruses on the climate, there is limited information about their structure and replication. Here we show that the dsDNA genome inside the EhV-201 virion is protected by an inner membrane, capsid, and outer membrane decorated with numerous transmembrane proteins. The virions are prone to deformation, and parts of their capsids deviate from the icosahedral arrangement. EhV-201 virions infect E. huxleyi by using their fivefold vertex to bind to a host cell and fuse the viruss inner membrane with the plasma membrane. Whereas the replication of EhV-201 probably occurs in the nucleus, virions assemble in the cytoplasm at the surface of endoplasmic reticulum-derived membrane segments. Genome packaging initiates synchronously with the capsid assembly and completes through an aperture in the forming capsid. Upon the completion of genome packaging, the capsids change conformation, which enables them to acquire an outer membrane by budding into intracellular vesicles. EhV-201 infection induces a loss of surface protective layers from E. huxleyi cells, which allows the continuous release of virions by exocytosis. Our results provide insight into how EhVs bypass the surface protective layers of E. huxleyi and exploit the organelles of an infected cell for progeny assembly.

molecular biology↗