L14 - GL Smith - Consequences of viral infection Flashcards
(63 cards)
describe how negative strand ssRNA replicates.
RNA-dependent RNA polymerase encoded by the virus converts -ve mRNA to mRNA
replicaction and transcription occur (producing more -ve mRNA to be put into new vesicles
-ve ssRNA - is purified virus RNA infectious?
no
regarding -ve strnad ssRNA:
Most of these viruses replicate in the _____, but __________ _______ replicates in the nucleus.
Most of these viruses replicate in the cytoplasm, but influenza virus replicates in the nucleus.
describe how influenza is a unique -ve sense ssRNA strand.
it requires host DNA-dependent RNA polymerase II as well as the virus RNA polymerase to make virus mRNAs
describe +ve strand ssRNA viral replication
genome = mRNA
- translation - to yield RNA dependand RNa polymerase
- repliacets genome via -ve RNA (which is then copied again
is purified viral RNA infectious if introduced into a susceptible cell?
yes
redcribe retroviruses’ replication
- genome = +ve ssRNA
- copied by reverse transcriptase to dsDNA
- integrated into host genome
- mRNA transcribed by host DNa dependant polymerase II
labe
in retrovirusess - where does the original reverse trancriptase come from?
in packaged weithin the vesciel
describe how dsDNA viruses replicate?
- in nucleus
- genome transported into nucleus
- Transcription uses host DNA- dependent RNA polymerase II.
for ds DNA viruses - is there a nuclease present in the viral particle?
what does this mean for infectivity?
no nucleic acid polymerase.
if the viral DNA makes its way to the nucleus - replication will occur
The viral DNA alone is infectious.
whihc dsDNA viruses replicate in the cytoplasm?
describe temporal control for viral gene expression
describe quantitative control for viral gene expression
how do +ve ssRNA express thier proteins from 1 RNA?
# translate genome = giant polypeptide proteolytic cleavage - cuts it up into the final proteins
The ______ single mRNA must encode all virus proteins. How? Translate the mRNA into a single giant polypeptide (a ‘polyprotein’) that is post-translationally cleaved by proteases into several, smaller, mature polypeptides.
The poliovirus single mRNA must encode all virus proteins. How? Translate the mRNA into a single giant polypeptide (a ‘polyprotein’) that is post-translationally cleaved by proteases into several, smaller, mature polypeptides.
do retroviruses also use polyprotein processing?
yes - to produce their mature capsid proteins from a polyprotein that is translated from a single mRNA.
Post translational cleavage of large polypeptides into smaller individual proteins is an important feature of many viruses - particularly ______ viruses.
Post translational cleavage of large polypeptides into smaller individual proteins is an important feature of many viruses - particularly RNA viruses.
host or virus codes for proteases responsible for polyprotein cleavage
often virus encoded = chemotherapy targets
does influenza use poly protein cleavage?
a genome with several different RNA segments, each encoding a different polypeptide (e.g., influenza).
do retroviruses also use splicing?
yep
Retroviruses use splicing to place the coding region for some proteins at the mRNA 5’ end. Thus ribosomes select this as they scan the mRNA from the 5’ end.
