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Virology-Polyomaviridae
exam 6
18
Microbiology
Undergraduate 4
11/05/2012

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Term
History of Mouse
Definition
infected animals with murine leukemia viruse and they developed tumors
Term
History of SV40
Definition
discovered as contaminant in cell cultures used for human poliovirus vaccines. resistant to formalin and in permissive cells it undergoes lytic. not a tumor inducing virus in its natural host
Term
virion structure
Definition
nonenveloped, VP1, 2, 3,
ds circular DNA with cellular histones
resistant to heat, formalin, and lipid solvent
beads on a string
Term
functional regions of virus genome
Definition
early, late, regulatory
Term
regulatory
Definition
promoters
drive transcription of mRNA
one direction around DNA
bidirectional synthesis of mRNA
ori
poly A recognition sequence
Term
overview of replication cycle
Definition
1. binds to receptor
2. enters cell via endocytic entry via caviolin, goes through ER, genome to nucleus
3. early gene expression; necessary to drive host cell into S phase, increase in amount of proteins necessary for DNA replication
Host RNA Pol II
4. DNA replication
5. late gene
6. assembly and release
Term
Temporal gene expression
Definition
Promoter for early genes encodes for mRNA which is spliced; one is large T and one small T

TATA box in promoter region binds necessary proteins to drive transcription
Term
Regulatory region
Definition

1. ori overlaps

2. sp1 binds to bp repeated region

binding controls expression of large T

3. requires specific transcription factors provided by host cell

4. enhancer region binds transcription factors

Term
Small T Ag function
Definition
Binds to PP2A and inactivates PP2A
(PP2A is a phosphatase that down regulates cell signaling pathways. mitogen-activated kinase pathway)
stimulates transcription
Term
MAP kinase pathway
Definition
when MAP gets activated it phosphorylates AP1 (AP1 is cellular transcription factor)

AP1 binds to promoters and stimulates transcription
Term
Large T Ag function
Definition
Binds to Rb
E2F is dissociated and binds to DNA

Drives cell to S phase

can inactivate p53 tumor suppression
Term
p53 tumor suppression
Definition
transcription factor

DNA damage leads to rapid induction of p53

promotes G1/S arrest

apoptosis

stops cell from dividing to allow repair
Term
p53 activates transcription of ______
Definition
p21

p21 blocks cell cycle progression
Term
genome replicaton
Definition
1. Large T binds to ori and allows bidirectional replication
2. recruites cellular polymerase
3. association of topoisomerase to introduce nicks in DNA to relax to continue replication
4. Large T forms 2 hexamers and binds to specific sites in ori. prevents further expression of early genes
5. has helicase acitivity and associates with DNA pol
Term
Replication vs. transformation
Definition
1. permissive cells allow viral replication and then lysis
2. nonpermissive cells don't allow viral replication. primase does not inteact correctly. no change from early gene to DNA replication. causes over abundance of large and small T--transofrmation because p53 inactivated and causes tumor and cancer
Term
Mouse polyomavirus

encodes how many antigens?
and which one intitates transformation?
Definition
three antigens (L,S,M)

middle interacts with membrane proteins to initiate cellular transformation

forces Src (Tyr kinase) into active conformation

Term
SV40

Transmission/shed

symptomatic?
Definition
inhalation and shed in urine (kidney)

in natural host (primates): persistent and asymptomatic

Term
BK virus

Definition
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