Читать книгу Principles of Virology - Jane Flint, S. Jane Flint - Страница 265

 Viral RNA genomes must be copied to provide both genomes for assembly into progeny virus particles and mRNAs for the synthesis of viral proteins.

 Viral RNA genomes may be naked in the virus particle [typically (+) strand RNAs] or organized into nucleocapsids in which proteins are bound to the genomic RNAs.

 Viral RNA-dependent RNA polymerases, like the other three types of nucleic acid enzymes, resemble a right hand consisting of palm, fingers, and thumb domains, with the active site located in the palm.

 Some viral RNA polymerases can initiate RNA synthesis without a primer, while others are primer dependent.

 Primers for viral RNA polymerases may be capped fragments of cellular pre-mRNAs or protein-linked nucleotides.

 Specificity of viral RNA polymerases for viral RNAs is conferred by the recognition of RNA sequences or structures.

 Host cell proteins are required for the activity of viral RNA polymerases.

 The single-stranded RNA genome of hepatitis delta virus is copied by host cell DNA-dependent RNA polymerase, an exception to the rule that RNA viruses are copied by RNA-dependent RNA polymerases.

 Viral RNA synthesis takes place in specific structures in the cell, either nucleocapsids, subviral particles, or membrane-bound replication complexes.

 RNA synthesis is error prone, and this process, together with reassortment and recombination, yields diversity that is required for viral evolution.