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DNA RNA Protein synthesis AMINO ACIDS PROTEIN Protein - - PowerPoint PPT Presentation
DNA RNA Protein synthesis AMINO ACIDS PROTEIN Protein - - PowerPoint PPT Presentation
DNA RNA Protein synthesis AMINO ACIDS PROTEIN Protein degradation FUNCTION Some properties of intracellular protein degradation (1970). Abnormal proteins are rapidly eliminated. Normal proteins are selectively degraded at widely
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Some properties of intracellular protein degradation (1970).
- Abnormal proteins are rapidly eliminated.
- Normal proteins are selectively degraded at widely different rates.
- Levels of specific proteins in animal cells can be regulated by
changes in rates of synthesis or rates of degradation (Schimke, 1970).
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Hershko & Tomkins JBC 1971
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Ciechanover, Hod & Hershko, BBRC 1978
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APF-1 (ubiquitin) Protein (µg) 1.5 3 7 PNAS 1980
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ATP lysozyme (µg)
- +
+ + + +
0 0 5 10 25 5 5
125I-ubiquitin 125I-lysozyme
lysozyme- (Ub)n
Hershko et al., PNAS 1980
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PNAS 1980
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DUB DUB DUB E2 E2 E2 Protein Protein E3 E3 Ub Ub Ub Ub Ub Ub Ub Ub Ub Ub Ub Ub Ub Ub Ub Ub Ub Ub E2 E2 E2 E1 E1 E1 Ub Ub E1 E1 E1 +ATP +ATP Ub Ub AMP+PP AMP+PPi
i
E1 E1 E1 E2 E2 E2 Ub Ub
+ +
ATP ATP ADP+P ADP+Pi
i
Protein Protein degraded degraded 26S proteasome 26S proteasome Ub Ub Protein Protein UCH UCH UCH
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Hershko et al., JBC 1983
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Substrate Yes No Yes No Yes Yes E3α-125I-protein cross-link
125I-protein
C y t
- c
h r
- m
e c ( y e a s t ) Cytochrome c (mammalian) L y s
- z
y m e R i b
- n
u c l e a s e A ( n a t i v e ) Ribonuclease A (oxidized 1) Ribonuclease A (oxidized 2)
DETECTION OF E3-SUBSTRATE BINDING BY CHEMICAL CROSS-LINKING Free 125I-proteins JBC 1986
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MBC 1995
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Cyclosome/APC
MBC 1995
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U U U U U U U U
Cdk1
Cyclin B
Cdk1
Cyclin B
Cdk1
~ ~ ~ ~ ~ ~ ~ ~
Cdc20
P P Inactive Cdk1 Inactive APC/cyclosome Active APC/cyclosome E 1 , E 2
- C
A T P , U b ( b )
ATP
(a) Cyclin synthesis 26S Proteasome Active Cdk1
Phosphatase
(d) Cyclin degraded Pi P P
Cdc20
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APC/C inactive APC/C active APC/C inactive APC/C = Anaphase-Promoting Complex/Cyclosome
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G0/G1 Time Time Level Level S p27 Cyclin E Cyclin A Skp2 p27 Cyclin E Cdk2 Cyclin E Cdk2 Cyclin A Cdk2 Cdk2 inactive Cdk2 active p27 degraded Cks1
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NCB 1999
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NCB 1999
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The three binding sites of Cks1
Cdk binding (green) Anion binding (blue) Skp2 binding (red) JBC 2002
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p27 Cyclin E Cdk2 p27 Cyclin E Cdk2 Cyclin E Cdk2
Cdk2 inactive p27-(Ub)n
P p27 Cyclin E Cdk2 Skp1 SCF complex P Skp2 & Cks1 synthesis Skp2 Cks1 Cyclin E synthesis
Cdk2 active p27 degraded
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Some roles of ubiquitin-mediated protein degradation.
- Control of cell division
- Signal transduction
- Regulation of gene expression
- Responses to inflammation
- Immune response
- Embryonic development
- Apoptosis
- Circadian clocks
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Some regulatory proteins degraded by the ubiquitin system. Regulator Role of degradation Examples
I
Positive Limitation of duration Cyclins (G1, S, M- phase); transcription factors (myc, fos…)
II
Negative Initiation of process Cdk inhibitors Anaphase inhibitor IκB transcriptional regulator
III
Positive or negative Activation by stabilization p53 tumor suppressor; β-catenin Type
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2000 Microbe hunters Vitamin hunters Enzyme hunters Gene hunters 1900
Arthur Kornberg : For the Love of Enzymes (1989)
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Technion lab (1971-present) Dvora Ganoth Hanna Heller Esther Eytan Sarah Elias Clara Segal Judith Hershko Former graduate students Aaron Ciechanover Yuval Reiss Valery Sudakin Shirly Lahav and many others… Collaboration and help Irwin A. Rose Leonard Cohen Joan Ruderman Michele Pagano Present graduate students Gil Bornstein Danielle Sitry-Shevah Yakir Moshe
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