Cellular Transforming Processes

1
Cellular Transforming Processes Sensed by
Apoptin
Dongjun Peng
Dept. of Biological Chemistry, LIC Leiden
University, The Netherlands Dept. of
Biochemistry Molecular Biology Tongji Medical
College, HUST, Wuhan, China
2
Apoptin
Phosphorylation
in human normal cells
dead
alive
3
Model system SV40 T antigen induces transforming
processes
N localization
SV40-T
apoptin
apoptin
apoptin
apoptin SV40-T
Phosphorylation
apoptin
P-apoptin
SV40-T antigen can be used to identify the
cellular factors involved in apoptin activation
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SV40 LT/st harbors transforming domains targeting
cellular factors
N-terminal of LT/st is sufficient for apoptins
activation
Rb binding
136aa
J
LT136
nls
Hsc70 binding
st unique
J
174aa
st
PP2A binding
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Is nuclear targeting of LT136/st important?
LT136/st
Control

• Rb is only involved in bringing LT/st into
  nucleus
• Nuclear targeting is essential

P-apoptin
apoptin
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Are both LT136 and st of importance?
PP2A
174aa
st
J
binding
Both LT136 and st are needed for optimal
activation of apoptin
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Is the J domain important for apoptins
activation?

D44N mutation in J domain
Both J-domains are involved in apoptin activation
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Is the PP2A binding domain in st crucial?
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Nuclear presence of both J domain PP2A binding
domain are crucial for activation of
tumor-related kinase

• Recently Both the J domain PP2A binding
  domain of st contact and inactivate PP2A

Chen Y, 2007, Nat Struct Mol Biol Cho US, 2007,
PLoS Biology
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Is inactivation of PP2A sufficient to activate
apoptins tumor-related kinase?
RNAi analysis
control
B56-?
RNAi
B56?
P-apoptin
apoptin
11

• Inactivation of PP2As regulatory subunit B56? is
  sufficient to activate apoptins tumor-related
  kinase

12
Acknowledgement

• Dept. of Biological Chemistry in University
  Leiden
• Mathieu Noteborn
• Maarten de Smit
• Patrick Voskamp
• Rhyenne Zimmerman
• Dept. of Molecular Genetics in University Leiden
• Claude Backendorf
• Ying-Hui Zhang
• Wilbert Vermeij
• University of Pittsburgh
• James Pipas

KNAW
Leiden Institute of Chemistry
Tongji Medical College