L9 - HPV (1) Flashcards
How are PVs classified?
sequences of the L1 major capsid protein
What are Alpha-PVs?
mucosal
ano-genital cancers
Examples of Alpha-PVs?
HPV16
HPV18
What are Beta-PVs?
cutaneous
non-melanoma skin cancer
How is the HPV genome organised?
all ORFs located on 1 strand of the DNA
10 ORFs - Early or late
LCR - contains origins of DNA replication, TFs
When are Early genes expressed?
in non-productive infected cells
non-structural proteins to reconfigure environment
When are late genes expressed?
in productively infected cells
structural proteins - capsid
E1?
helicase
initiate DNA replication
E2?
transcriptional regulation
DNA replication
E4?
late early protein
virus assembly/release
E5?
Oncoprotein and genome amplification
E6/E7?
Oncoprotein and cell cycle modulation
L1
Major capsid protein
L2
Minor capsid protein
What is the HPV life cycle dependent on?
keratinocyte differentiation
What happens when a cell detaches from the basement membrane?
switch in transcriptional programme
drastic morphologial change
withdraw from cell cycle
dead cell - gets rid of organelles - makes physical barrier of epithelium
HPV hijacks this process
How to culture HPV?
dermal equivalent collagen matrix with culture media on top
dispersed primary keratinocytes
creates a differentiating epithelium
How does HPV enter cells
disassembly of capsid - exposure of genome within endosome
L2 - retromer complex - genome into cytoplasm
enter nucleus - colocalise at PML bodies
AVOIDS DETECTION BY IMMUNE SYSTEM (cGAS)
How is PV transcription complex?
multiple promoters
alternate splice patterns
differentiation of mRNA production
What is the PV early promoter?
P97 -UNDIFFERENTIATED CELLS
expressed E6, E7
What is the PV late promoter?
differentiation-dependent = P670
E4/L1/L2 (E1)
How is Transcription regulated in PV?
Cis elements
LCR contains enhancer elements
What binding sites does the LCR contain?
binding sites for E2 protein
What do E2 regulatory proteins contain?
sequence-specific DNA binding & dimerisation domain - carboxyl terminus
transactivating domain - amino terminus
What does PV replication require in cis and trans?
cis - DNA ORI
trans - E1, E2
What does the efficient replication of PV depend on?
association of E1 and the S-phase specific cyclin E complex
E2 stabilised he E1-Ori interaction
Job of E1 in PV replication?
bring in rest of host cell replication machinery
functions at ATP-dependent helicase
Why is driving the cells into S-phase necessary?
allow viral DNA replication in the stratified epithelium in a PROLONGED G2 PHASE
suprabasal cells usually exit cell cycle & differentiate - in E5/E6/E7 expressing cells - terminal differentiation delayed
What do late functions include?
vegetative DNA synthesis
capsid protein synthesis
virion assembly
EXCLUSIVE TO DIFFERENTIATED KERATINOCYTES
GOOD FOR IMMUNE EVASION
accumulated of the late early gene E4
What happens during PV assembly and release?
accumulation of late gene products
move L2 to nucleus - associated with PML bodies
L1 as capsomeres in cytoplasm - translocate to nucleus - interact with L2 and PMLs
encapsidation??
E4 protein disrupts keratin network - effect integrity of cornified envelope
