From The Medical Microbiology, University of Capetown

1
Human Papilloma Virus (HPV)
Over 100 Different Subtypes (80 Fully Sequenced)
High Ovarian Cancer Risk Associated With Types
16, 18, 31, 33
From The Medical Microbiology, University of
Capetown
2
A typcial HPV Genome
http//cinvestav.mx/genetica/MyFiles/Papillomaviru
s/PAPgeno.htm
3
Genes of Human Papilloma Virus
Early Genes E1 Viral replication maintains
episome E2 Transcriptional regulation,
co-factor for viral replication E4 Disrupts
cytokeratins E5 Interacts with growth factor
receptors E6 Transforming protein p53
degradation E7 Transforming protein Rb
binding Late Genes L1 major capsid
protein L2 minor capsid protein
4
Transformation is Caused by Viral Integration
Viral Integration Not part of normal viral
life-cycle Occurs randomly in host
chromosomes Characteristic breakpoint in viral
genome E1-E2 disruption (i.e. disrupts viral
replication) Abnormally regulated E6/E7
expression Associated with oncogenesis but not
required
5
http//www.cineca.it/networking/streaming/sestri/c
ourses/cancgen/Bernards.htm
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HPV E6 and E7 Cooperate to Transform Cells
7
HPV16 E6 and E7 Cause DNA Damage (to Persist)
E6/E7 may cause DNA damage
E6/E7 may allow cells to accumulate DNA
damage (i.e. checkpoint failure)
From Duensing and Munger (2001) Cancer Research
627075
8
HPV16 E6 and E7 Induce Multiple Centrosomes
HPV 16 Positive Human Tumor Preparations
Cultured NHK Cells Expressing HPV16 E6 and/or E7
From Duensing et al. (2000) PNAS 9710002
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HPV16 E6 and E7 Cause Mitotic Errors
From Duensing et al. (2000) PNAS 9710002
10
HPV16 E7 Induction of Multiple Centrosomes is an
Early Event
HPV16 E7 Destabilizes pRB
Percent of Mononucleated Cells with Extra
Centrosomes
Centrosomes Chromosome 11
Percent of Cells with 2 Copies of CHR 11 with
Extra Centrosomes
From Duensing et al. (2001) Cancer Research
612356
Extra Centrosomes Appear Before Aneuploidy in E7
Expressing Cells
11
HPV16 E6 Induction of Multiple Centrosomes is a
Late Event
HPV16 E6 Destabilizes p53
Multinucleate
Binucleate
E6-expressing cells with multiple centrosomes are
aneuploid Aneuploidy occurs before the appearance
of extra centrosomes in E6-Expressing cells
From Duensing et al. (2000) PNAS 9710002
12
HPV16 E6 Induction of Multiple Centrosomes is a
Late Event
HPV16 E6 Destabilizes p53, E7 Destabilizes pRB
E6
E6-expressing cells with multiple centrosomes are
aneuploid Aneuploidy occurs before the appearance
of extra centrosomes in E6-Expressing cells
From Duensing et al. (2001) Cancer Research
612356
13
Polyploid Cells With Extra Centrosomes Arise
through Cytokinesis Failures
http//home.ccr.cancer.gov/metabolism/kleeccr.htm
From Kyung Lee, Center for Cancer Research, NCI,
NIH
14
Polyploid Cells With Extra Centrosomes Arise
through Cytokinesis Failures
Cytokinesis
Two Euploid Cells
Cytokinesis Failure
Polyploid Cell
Adapted from http//www.world-builders.org/lessons
/less/les4/mitosis.html
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Polyploid Cells With Extra Centrosomes Arise
through Cytokinesis Failures
Three Dead Cells
?
Polyploid Cell
Adapted from http//www.world-builders.org/lessons
/less/les4/mitosis.html
16
HPV16 E6 and E7 Cooperate to Induce Aneuploidy
DNA Chromosome 11
From Duensing et al. (2000) PNAS 9710002
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HPV16 E6 and E7 Cooperate to Induce Aneuploidy
E7 inhibits pRb and p21 -allows activation of
E2F targets (Cdk2, Cyclin E, Cyclin A)
-causes extra centrosome duplication
Extra Centrosomes Cause Mitotic Failures
E6 inhibits p53 -causes checkpoint failures
-causes cytokinesis failures -produces
polyploid cells with extra centrosomes
From Duensing and Munger (2001) Biochem. et
Biophys. Acta. 1471M81
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HPV16 E6 and E7 Cooperate to Induce Aneuploidy
E6 Binds to p53, de-regulates checkpoints frequen
t failure to arrest at G2 due to DNA
damage frequent failure of cytokinesis generates
polyploid cells with multiple centrosomes E7
Binds to pRb, de-regulates cell cycle
transcription induces centrosome
over-duplication causes mitotic
abnormality mitotic abnormality in polyploid
cells leads to genetic instability and
aneuploidy
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Centrosomes and Genetic Stability
A cell forced to over-duplicate centrosomes by
overexpressing Mps1
Overexpression of Mps1 causes Mitotic
Abnormalities Is Mps1 an oncogene?
/
Microtubules
Centrosomes
Kinetochores
DNA