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37 Cards in this Set

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briefly describe attachment of virus to host cell.
it is an ionic interaction with the cell surface "receptor" not enzymatic in nature, occurs over wide variety of temps, and number and nature of receptors on cell varies
briefly describe viral penetration of the host cell.
via viropexis or fusion )only enveloped viruses), requires energy and is temp dependent
briefyly describe the uncoating process in viral infections.
envelope and in some cases the capsid is removed so that the genome can be expressed, if virion enters via viropexis, the internal fusion step with the endosome or lysosome mediates the uncoating
when do virions that penetrate via viropexis undergo fusion?
internal fusion with endosome or lysosome at low pH
what viruses will use viropexis?
all non enveloped and some enveloped viruses
how does herpes penetrate the cell?
via fusion mediated by specefic viral peplomers that have fusogenic domains and fusion is temp dependent
when does adenovirus uncoat?
not traditional uncoating, loses some capsid I think... but leaves most of it and attaches to nuclear membrane and "squirts" its DNA in there... not sure on this, look it up on NTS
what DNA viruses use cellular DNA polymerases?
parvoviruses, polyoma, and papilloma
which DNA viruses use a viral encoded DNA polymerase?
adenovirus, herpesvirus, poxvirus
how does hepadnavirus replicate?
unique, it is DNA (partially DS that is corrected to full DS in nuc) then txned by host RNA poly to RNA then uses a viral encoded reverse transcriptase (in developing cytoplasmic virion particle) to go back to DNA
describe the sequential events of gene regulation and expression in Herpes.
first txn of immediate early protein, IE protein binds to cis element and causes txn of early genes. early genes will cause txn of other factors that will join with IE and other proteins to transcribe late genes
what DNA virus replicates in the cytoplasm and how?
poxvirus via viral encoded DNA polymerase
describe briefly the replication of RNA + viruses.
genomic RNA is mRNA, first it is transcribed, there is no RNA pol in the virion, it is translated. This viral encoded RNA pol copies + RNA to a neg RNA template which serves as the template for copying genomic + RNAs
briefly describe replication of Neg stranded RNA viruses
first event after uncoating is txn via a viral RNA pol wi the virion. then the mRNAs are translated. genomic RNA is not infectious. genomic RNA is then copied to plus RNA template and this template is used to make genomic neg RNA daughters
what are the actions of the reverse transcriptase of retrovirus?
RNA dependent DNA pol, RNase, and DNA dependent DNA pol (makes SS to DS DNA)
describe the replication events of retroviridae briefly.
reverse transcriptase replicates each SS RNA to SS DNAs in the virion, then uses its RNAse activity, then copies the SS DNAs to DS DNAs. now we have the DS DNA provirus which integrates into the host genome via the LTR segments on each end (can cause oncogenes). Transcribed by host RNA pol II which can become dimerized to the daughter genome, translated to proteins or spliced and then translated.
what are the actions of the retroviral drugs?
4 classes: block fusion, block RNA to DNA activity (2), and block protease activity of the viral "pre" proteins
briefly describe events of encapsidation
capsid proteins self assemble, some icos capsids assemble first and then get filled with genome. helical capsids proteins are associated with the daughter genomic RNA as it is being synthesized. some have complex processes like poxvirus in the cytoplasm
how do viruses with an M protein envelope?
M proteins associate with the cytoplasmic domain of the peplomers in the membrane and then the capsid interacts with the M protien to trigger budding.
how do viruses without an M protein envelope?
capsid interacts with the cytoplasmic domain of the peplomer inserted into the cell membrane to triggerbudding.
how do herpes viruses obtain their envelope? poxviruses?
herpes gets an initial envelope from the inner nuclear membrane which interacts with tegument. it may then de-envelope and acquire the envelope from the ER. Pox viruses get several layers of envelope
describe retrovirus morphology in terms of envelopes.
A type virion particles migrate through the cytoplasm and get enveloped at the PM forming B type particles. C typ particles form at the PM, do not migrate through the cytoplasm as intact particles
look at chart on slide 26 in lecture 60, where do most RNA viruses replicate?
in the cytoplasm
what is the eclipse phase of viral reproduction?
when there are no infectious particles present: penetration, attachment, replication, etc
what do cells provide to the replicating virus?
structural support, ribosomes, transacting factors, amino acids, nucleotides, lipids, energy
describe the phases of DNA virus replication using the drugs cyclohexamide and Phosphonoformic acid (PAA).
CH blocks protein synth and PAA blocks viral replication. with CH see only IE genes, with PAA see IE genes and proteins, E genes and proteins but no L genes or proteins.
review: what are the DNA viruses and their features?
Herepes: DS linear, icos with envelope. Hepadna is paritally DS circullar, icos with envelope. Adeno is DS linear, icos, no envelope with fibers. Polyoma is DS circular, icos no env. papilloma is DS circular, icos, no env. Parvo is SS linear icos, no env. Pox is DS linear, complex with multi layered envelope
what are the immediate early events (not genes/proteins) of enveloped DNA virus (eg Herpes)?
attachment (receptor/cell specefic mediated by glycoprotein), penetration (fusion), capsid migration to nucleus (note in herpes teguement is in cytoplasm and can go to nucleus and thus may play a role in viral gene product formation by being a transactivator but not viral attachment), viral txn occurs
describe the immediate early events of non enveloped DNA viruses.
attachment via capsids, penetration via endocytosis, migration to nucleus and txn.
describe the txn and tsln of IE genes in DNA viruses.
in both enveloped and non enveloped viruses, capsid is at the nucleopore and disintegrates and the DNA goes into the nucleus and txned by cell RNA pol II, viral mRNA goes to cytoplasm and tsln occurs
role of viral IE proteins?
get the cell ready for viral DNA replication and act as trans factors for E genes
role of DNA virus E proteins?
make enzymes for direct DNA synthesis, all of em encode a viral DNA pol, herpes has a thymidine kinase in there too. Also act as trans factors for late genes
role of Late proteins?
basis of mature virion (assembly genes). capsids, glycoproteins. Also act as transactivators for other late proteins.
describe enveloped vs non enveloped DNA virion cell release?
enveloped aquiring an envelope and keep it as they leave whereas nonenveloped aquire an envelope from the nucleus (usually) and it is "lost in the cell as the virion leaves, note non envelope release usually causes cell lysis
describe herpesvirus virion assembly.
replicates in nucleus thus makes capsids in nucleus, capsid buds through the nuclear membrane and gets an envelope, loses the envelope, gets an envelope in the golgi and exits, can either lyse or not lyse cell when exits.
describe Hepadnavirus replication.
envelope fuses with membrane, capsid migrates to nucleus, genome enters and forms covalently closed circular DNA from its partilly DS genome (thus replication in the nucleus). Txn forms large message and small message. Large RNA txn the P (polymerase protein - a reverse transcriptase), txn capsid proteins, and serves as the template for the DNA genome (thus DNA replication ALSO in the cytoplasm). Small RNA's are for glycoproteins and things to that go in the envelope. The mature virion forms in the cytoplasm and it gets it envelope from the golgi.
describe poxvirus replication.
note its gene products are called early, intermediate and late. Probly enters via fusion. everything takes place in the cytoplasm. It contains a DNA dependent RNA pol that will then synthesixe early mRNA once the core is in the cytoplasm. These genes include growth factors and host immune defense systems. Early gene synthesis induces a second uncoating in which a nucleoprotein complex with the genome is released. Early gene expression is inhibited. Genome is replicated via early proteins and these replicates serve as templates for further replication or as templates for txn of intermediate genes. These serve as transactors for late genes. Late genes make stuff needed for assembly. Immature virion assembles and gets the double membrane from the golgi complex at can exit the cell.