PMID- 10323868
OWN - NLM
STAT- MEDLINE
DCOM- 19990604
LR  - 20190516
IS  - 0890-9369 (Print)
IS  - 0890-9369 (Linking)
VI  - 13
IP  - 9
DP  - 1999 May 1
TI  - Ubiquitination of p27 is regulated by Cdk-dependent phosphorylation and trimeric 
      complex formation.
PG  - 1181-9
AB  - The cellular abundance of the cyclin-dependent kinase (Cdk) inhibitor p27 is
      regulated by the ubiquitin-proteasome system. Activation of p27 degradation is
      seen in proliferating cells and in many types of aggressive human carcinomas. p27
      can be phosphorylated on threonine 187 by Cdks, and cyclin E/Cdk2 overexpression 
      can stimulate the degradation of wild-type p27, but not of a threonine
      187-to-alanine p27 mutant [p27(T187A)]. However, whether threonine 187
      phosphorylation stimulates p27 degradation through the ubiquitin-proteasome
      system or an alternative pathway is still not known. Here, we demonstrate that
      p27 ubiquitination (as assayed in vivo and in an in vitro reconstituted system)
      is cell-cycle regulated and that Cdk activity is required for the in vitro
      ubiquitination of p27. Furthermore, ubiquitination of wild-type p27, but not of
      p27(T187A), can occur in G1-enriched extracts only upon addition of cyclin E/Cdk2
      or cyclin A/Cdk2. Using a phosphothreonine 187 site-specific antibody for p27, we
      show that threonine 187 phosphorylation of p27 is also cell-cycle dependent,
      being present in proliferating cells but undetectable in G1 cells. Finally, we
      show that in addition to threonine 187 phosphorylation, efficient p27
      ubiquitination requires formation of a trimeric complex with the cyclin and Cdk
      subunits. In fact, cyclin B/Cdk1 which can phosphorylate p27 efficiently, but
      cannot form a stable complex with it, is unable to stimulate p27 ubiquitination
      by G1 extracts. Furthermore, another p27 mutant [p27(CK-)] that can be
      phosphorylated by cyclin E/Cdk2 but cannot bind this kinase complex, is
      refractory to ubiquitination. Thus throughout the cell cycle, both
      phosphorylation and trimeric complex formation act as signals for the
      ubiquitination of a Cdk inhibitor.
FAU - Montagnoli, A
AU  - Montagnoli A
AD  - Department of Pathology and Kaplan Comprehensive Cancer Center, New York
      University Medical Center, New York, New York 10016, USA.
FAU - Fiore, F
AU  - Fiore F
FAU - Eytan, E
AU  - Eytan E
FAU - Carrano, A C
AU  - Carrano AC
FAU - Draetta, G F
AU  - Draetta GF
FAU - Hershko, A
AU  - Hershko A
FAU - Pagano, M
AU  - Pagano M
LA  - eng
GR  - R01 GM057587/GM/NIGMS NIH HHS/United States
GR  - R37 CA076584/CA/NCI NIH HHS/United States
GR  - R01 CA076584/CA/NCI NIH HHS/United States
GR  - R01 CA76584/CA/NCI NIH HHS/United States
GR  - R01 GM57587/GM/NIGMS NIH HHS/United States
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - Genes Dev
JT  - Genes & development
JID - 8711660
RN  - 0 (Cell Cycle Proteins)
RN  - 0 (Cyclins)
RN  - 0 (Microtubule-Associated Proteins)
RN  - 0 (Tumor Suppressor Proteins)
RN  - 0 (Ubiquitins)
RN  - 147604-94-2 (Cyclin-Dependent Kinase Inhibitor p27)
RN  - EC 2.7.11.22 (Cyclin-Dependent Kinases)
SB  - IM
MH  - Cell Cycle
MH  - *Cell Cycle Proteins
MH  - Cell Division
MH  - Cell Line
MH  - Cyclin-Dependent Kinase Inhibitor p27
MH  - Cyclin-Dependent Kinases/*antagonists & inhibitors/chemistry/metabolism
MH  - Cyclins/chemistry/metabolism
MH  - G1 Phase
MH  - HeLa Cells
MH  - Humans
MH  - Microtubule-Associated Proteins/chemistry/*metabolism
MH  - Phosphorylation
MH  - Protein Conformation
MH  - Signal Transduction
MH  - *Tumor Suppressor Proteins
MH  - Ubiquitins/*metabolism
PMC - PMC316946
EDAT- 1999/05/14 00:00
MHDA- 1999/05/14 00:01
CRDT- 1999/05/14 00:00
PHST- 1999/05/14 00:00 [pubmed]
PHST- 1999/05/14 00:01 [medline]
PHST- 1999/05/14 00:00 [entrez]
AID - 10.1101/gad.13.9.1181 [doi]
PST - ppublish
SO  - Genes Dev. 1999 May 1;13(9):1181-9. doi: 10.1101/gad.13.9.1181.