Sequence-independent characterization of viruses based on the pattern of viral small RNAs produced by the host

RNA viruses are categorized into positive-strand, negative-strand, or double-stranded groups based on their genomic structure and replication mechanisms. This classification dictates how they exploit host cellular machinery for protein synthesis and replication. Some RNA viruses also utilize reverse transcription as part of their life cycle, further diversifying their replication strategies.Positive-Strand RNA VirusesPositive-strand RNA viruses have genomes that function directly as messenger...

Subviral agents are infectious entities that resemble viruses but lack one or more viral components, such as a capsid or essential replication machinery. These agents include viroids, prions, and satellites, each possessing distinct structural and functional characteristics that influence their mode of infection and replication.Viroids are the simplest subviral agents, consisting of circular, single-stranded RNA molecules without a protein coat. They exclusively infect plants, relying entirely...

Small interfering RNAs, or siRNAs, are short regulatory RNA molecules that can silence genes post-transcriptionally, as well as the transcriptional level in some cases. siRNAs are important for protecting cells against viral infections and silencing transposable genetic elements.
In the cytoplasm, siRNA is processed from a double-stranded RNA, which comes from either endogenous DNA transcription or exogenous sources like a virus. This double-stranded RNA is then cleaved by the...

Viral genomes exhibit remarkable diversity in size, structure, and composition, influencing their replication strategies and interactions with host cells. These genomes consist of either DNA or RNA and may be linear or circular. Additionally, they can be single-stranded or double-stranded, with each configuration affecting how the virus propagates within a host. RNA viruses, for instance, generally have smaller genomes than DNA viruses, a factor that contributes to their high mutation rates and...

The human body harbors a vast and diverse viral community known as the human virome. The virome includes bacteriophages that infect bacteria, and eukaryotic viruses that infect human cells. Transient dietary and environmental viruses also contribute to this dynamic ecosystem. Estimates suggest the human body may contain on the order of 10¹³ viral particles, though abundance varies widely by body site and detection method.Comprehensive characterization of the virome has become possible...

Archaeal viruses play a crucial role in the ecosystems of extremophilic archaea, particularly those belonging to the phyla Euryarchaeota and Crenarchaeota. By shaping host evolution and facilitating gene transfer, these viruses influence microbial communities and contribute to genetic diversity in extreme environments. The archaea they infect thrive in acidic hot springs and hydrothermal vents characterized by high temperatures and low pH. Archaeal viruses exhibit remarkable structural...