SV 40 Flashcards
1
Q
Stages
A
Attachment Penetration Uncoating Early Gene Expression Genome Replication Late Gene Expression Assembly Release
2
Q
Attachment
A
- receptor mediated
- VP1 attaches to MHC 1
3
Q
Penetration
A
- endocytosis by caveolae
- caveolae not acidified but instead fuse with ER membrane so virions enter ER lumen
4
Q
Uncoating
A
- virus binds to receptor on lumens face on ER membrane
- binding triggers a conformational change that creates an injection port through the ER membrane
- viral minichromosomes diffuse into cytoplasm and then imported into the nucleus due to NLS signals from the histones
5
Q
Early Gene Expression
A
- DdRp II transcribes primary transcript
- the primary transcript covers the early part of the genome
- capped and polyadenylated
- differential splicing occurs producing mRNAs for T-Ag and t-Ag
- the early mRNAs are exported into the cytoplasm and translated
- T-Ag protein has NLS and is imported into the nucleus
6
Q
Genome Replication
A
- T-Ag sends host cell into S-phase of cell cycle by binding to cellular proteins RB and p53
- T-Ag interacts with host DNA replication proteins (made during S-phase) and re-targets them to SV origin (T-Ag acts as a modifier subunit - hijacking)
- T-Ag has DNA helices activity that unwinds dsDNA at origin and host factors take over
- Viral genome is replicated bidirectionally (theta mode)
7
Q
Late Gene Expression
A
- T-Ag represses early gene expression and activates late gene expression
- A single primary transcript is produced, capped, and polyadenylated covering the late region of the genome
- late mRNAs exported to cytoplasm and translated
- differential splicing occurs generated mRNAs for agnoprotein/VP1 and VP2/VP3
- Leaky scanning occurs to produce (VP2/3 complex) and/or efficient reinitiation of translation to produce (agnoprotein/VP1) required
- all late proteins have NLS and are imported into nucleus
8
Q
Assembly
A
- agnoprotein facilitates nuclear localized of VP1 and capsid assembly
- occurs in nucleus via nucleation of pentamers around SV40 minichromosome
9
Q
Release
A
cell lysis
