RNA Virus Replication Flashcards

1
Q

General comments

A

*Replicate in the cytoplasm of the cell except for orthomyxoviruses (e.g., influenza virus and retroviruses [e.g., HIV])
*Single-stranded (s.s.) RNA viruses have either a positive (+) sense (messenger polarity), negative (-) sense (antimessenger polarity), or ambisence polarity (both + and -)
*All negative-sense RNA viruses are enveloped
*Since cells lack cytoplasmic RNA polymerase, RNA viruses must produce their own replicase/transcriptase

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2
Q

RNA Virus Genome Replication

A

Negative sense RNA viruses have a replicase/transcriptase associated with the RNA within the virion
All s.s. RNA viruses except retroviruses replicate via a double-stranded RNA intermediate
Retroviruses have a nuclear phase, involving a reverse transcriptase in their genomic RNA replication
The spontaneous mutation frequency of RNA viruses is higher than the DNA viruses because their RNA polymerase are not as accurate in duplication

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3
Q

Expression of RNA Genomes

A

Transcription of orthomyxoviruses and retrovirus mRNA occurs in the nucleus
RNA viruses have developed unique mechanisms to produce individual polypeptides from polycistronic RNA since this is not a property of eukaryotic cells
– picornavirus synthesize polypeptides that are then cleaved by viral proteases
– individual initiation and termination signals appear throughout RNA of rabies virus

Each virus family has unique way of making necessary proteins. HIV synthesizes a long polypeptide and has a protease that cuts it for diff functions. This protease is key drug target.

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4
Q

expression of RNA Genomes, ctd.

A

All transcription begins on 3’ end, but polymerase slides over various size intervening sequences to yield transcript of various compositions and lengths
– Orthomyxoviruses and reoviruses have segmented genomes
– retroviruses have spliced transcripts
Some RNA viruses use a combination of strategies

Viruses that have segmented genome, each segment codes for single or maybe two polypeptides.

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5
Q

RNA Virus Table

A

Differ in all sorts of ways. …genome size,replication site, enveloped or not, morphology (shape) +/- sense.

- sense guys use replicase/transcriptase to make + sense to make mRNA to translate protein

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6
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