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28 Cards in this Set

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picorna, calici, astro, toga corona, flavi
general steps in replication of + stranded RNA viruses?
virions uncoat and genome goes to cytoplasm where tsln occurs to make enzymatic proteins including RNA pol. RNA genome is replicated to neg strand intermediate. Structural proteins are tslned for some families... packaging and leave the cell usually via lysis
pathogenically important picornaviruses?
enteroviruses (polio and kocksaci), rhino, kobu (aichi) causes gastroenteritis, hepato (hepatitis A and human parechvirus), apthovirus (foot and mouth)
how is the picornavirus genome organized?
polyprotein divided into three regions: P1 is viral capsid proteins, P2 and P3 encode for enzymatic proteins
in picornavirus what is the sequence outside the 5' area that is important in initiating transcription
IRES internal ribosome entry site
do picorna viruses have poly A tail?
yes
what is the VPg in the picornavirus?
viral protein genome linked to 5' end of genome
describe tsln of viral RNA of picornacirus.
VPg cleaved when RNA enters cytosol and ribosome binds IRES (instead of MG cap as in host mRNA). IRES causes cleavage of Tsln factors eIF4E thus all the host initiation factors now bind to the IRES secondary structured RNA of the picornavirus instead of 5' caps. Now all tsln is viral, not host
cleavages of the 1 polyprotein made from picorna RNA that occur immediately after txn? what is an example of differing functions of pre and post protease activity?
seperates the P1, P2, and P3. a protease and the pol are originally connected before a protease acts on it; this precursor protein has its own function in traveling to the nucleus and degrading host factors. It is later chopped up by the protease
how many progeny genomes are produced in each cell infected with picornavirus?
50,000
do picornaviridiae make more neg or pos RNA?
25 to 60X more positives.
describe most RNA pol error rates (picorna specefically)
high mutation rate - 1-2 NT per replication event
describe picornavirus assembly.
all picornaviruses have 4 structural proteins (VP1, 2, and 3 on outside while VP4 on inside), 1 copy of each join to form a protomer. 5 protomers form a pentamer which is one side of the virus. now the question is do all these form around the RNA or do they form and leave a little hole for the genome to squeeze through...? who knows???!?!?!
picornavirus effects on the cell?
replicate very rapidly, inhibit cell protein synth, reduce cell mRNA and rRNA synth, block host vesicle transporting so that cellular proteins are inhibited (cytokine secretion is blocked). cell membranes leak, cytoskeleton altered, nuc shrinks, membrane vesicles are formed in cytoplasm at site of virus replication, eventually cell lyses and virions are released.
what is the capsid and envelope status of picorna?
icos w/o envelope
what is the capsid and envelope status of flavivirus?
icos and enveloped
how are flaviviruses transmitted and what diseases do they cause?
transmitted via mosquitoes and ticks. Dengue, yellow fever, west nile, Hep C. also a pestvirus (infects animals)
describe the genome organization of flaviviruses.
similar to picorna, one polypeptide made, codes for structural proteins at 5' end of genome, non coding structural info at the 3' end. 5' cap is present, do not have IRES
describe the capsid and envelope status of the caliciviruses.
icos, non enveloped
genera of calicivirus and pathogenesis of them.
norovirus: norwalk virus (very common epidemic gastroenteritis causer). sapovirus: sapporo virus, pediatric gastroenteritis (more endemic cases). Lagovirus (rabbit killer), vesivirus (cat resp disease)
calicivirus genome organization?
VPg at 5' end, polyA tail at 3'. structural genes in 5' end, non structural in 3'. First whole thing translated to get nonstructural proteins (viral pol) then small subgenomic RNA (neg stranded) polymerized and tslned to make structural proteins. Thus multiple peptides tslned. Note the neg strand is the template for replication as well as the transcript for structural proteins
what are the two models for production of subgenomic RNA in calicivirus?
internal initiation on longer than subgenomic length minus strands. Premature termination during minus strand synth and thus shorter subgenomic plus strands
describe the capsids and envelope status of togavirus.
icos capsids, enveloped
togavirus genera and pathogenesis of them
alphavirus (arbovirus - insect vectors); sindbis: semliki forest, equine enceph which can go to ppl, and chikungunya; rubivirus causes rubella and arteriviruses do not hurt ppl
what is the togavirus genome organization?
non structurals in 5', structurals in 3', full length genomic and sub genomic particles that contain 5' cap structures thus tsln occurs on each.
replication scheme of togavirus?
similar to calici... 5' end tslned to get the RNA pol then RNA replication making full length and subgenomic RNAs. SGmRNA's make structurals.
describe the capsid and envelope status of the corona virus.
spherical (helical capisds). and envelope
describe coronavirus genome organization and life cycle events.
complicated... has 5' cap and poly A tail. structurals at 5' and non structurals at 3'. some non structurals interspersed with structurals. full length genome is tslned to make RNA pol, RNA replication then occurs, neg strand is used to make a whole set of smaller SGmRNAs, each SGmRNA makes either one or two proteins, in this fashion virus is made in a kintec way. get envoleped in golgi