Lec 9 - DNA virus replication Flashcards
What type of virus is in Baltimore group 1, what do they require and what do they have to induce?
- dsDNA viruses
- Require DdDp and DdRp
- Must induce S phase because human cells replicate too slowly
What are 3 possible results of a DNA virus infection?
- Lysis
- Transformation: can be a dead-end host
- Latent
Describe a typical dsDNA virus replication cycle
- Topoisomerase unwinds DNA at ori
- ssDNA binding proteins cover DNA
- RNA primase marks ssDNA with primers
- DNA polymerase synthesises new DNA
How does SV40 have bi-directional replication?
- Large T antigens form hexamer and 2 hexamers bind ori
- Hexamer’s helicase activity melts DNA
- Hexamers replicate in opposite directions: theta replication
What are the functions of p53 and RB?
- p53 induces apoptosis and inhibits transcription by preventing RB detaching from E2F
- RB is an S phase checkpoint that binds E2F to inhibit transcription
How does SV40 prevent apoptosis?
Large T antigen blocks p53 and interacts with RB to prevent transcription suppression
What is the function of SV40’s small t antigen?
Inhibits PP2A complex to prevent suppression of transcription genes
What disease does polyoma JC virus cause?
Progressive multifocal leukoencephalopathy (PML) which is a fatal demyelinating disease of the CNS.
What does HPV use to target p53 and RB?
Oncoproteins E6 and E7
How does HPV infect its target cells?
Infects basal layer of cervical epithelium via microtears. Ascends and transforms at surface
What are the high risk subtypes of HPV?
16 and 18
How do poxviruses infect cells and how are they an exception to dsDNA viruses?
Mimic growth factor ligands with vaccinia growth factor (VGF) to stimulate S phase.
Replicate in cytoplasm not nucleus
