Virology-Fall, 2015
5. Genome Expression and ReplicationRNA Viruses (October 15….)
Main Points and Concepts
RNA viruses have “objectives” that may be irrelevant to a cell but the viruses must play
by the cell’s rules.
Although RNA viruses are diverse, with many different types of templates, they all rely
on RdRp’s-which a cell does not normally have, and those RdRp’s have some
common features.
All viral RdRps make mistakes.
Secondary structure of the viral RNA is important.
Viral gene expression is closely linked to viral genome replication.
RNA viruses cannot take advantage of the host’s machinery for expression of genes
encoded in DNA.
To ensure that its genes are expressed, a virus must interact with host expression
machinery and sometimes subvert that machinery.
RNA viruses encode proteins with multiple functions.
.
Learning goals
Students will understand and be able to explain the terminology used to describe
genome replication and gene expression by RNA viruses.
Students will be able to recognize and describe the important themes and
mechanisms that characterize RNA virus gene expression and will be able to provide
examples to illustrate their understanding.
Students will be able to explain why certain viruses have adopted unusual strategies for
replication and expression.
Students will be able to compare and contrast theme and strategies for RNA virus gene
expression and replication.
Students will be able to explain how and why RNA viruses exhibit such a high error rate.
Students will be able to explain the evolutionary consequences of this high error rate.
Readings
Textbook Chapters 6 and 11 as follows:
Chapter 6: pp. 170-182, 195-198
Chapter 11: pp. 379-405
Interesting Web Sites With Some RNA Virus Information:
http://viralzone.expasy.org/all_by_species/1116.html
http://viralzone.expasy.org/all_by_species/1096.html
http://viralzone.expasy.org/all_by_species/1936.html
https://www.youtube.com/watch?v=yOEvN6bK4cA
http://virology-online.com/general/Replication.htm
http://www.microbiologybook.org/mhunt/rna-ho.htm
Some terminology associated with gene expression and replication of
RNA viruses
Template dependent
DNA dependent RNA polymerase
RNA dependent RNA polymerase (RdRp)
Replicase
Transcriptase
Helicase
Transcription (initiation, elongation, termination)
Promoter
Primer
Genomic RNA, virion RNA
Antigenomic RNA
Subgenomic RNA
ORF
RF and RI