SIAH-1 interacts with CtIP and promotes its degradation by the proteasome pathway.
SIAH-1 and SIAH-2 are the human members of an evolutionary highly conserved E3 ligase family. SIAH-1 is a p53 and p21(Waf-1/Cip-1) induced gene during apoptosis and tumor suppression. In stable-transfected clones of MCF-7 cells, SIAH-1 overexpression was associated with apoptosis, mitotic alterations and p21(Waf-1/Cip-1) induction of expression. Using a two-hybrid screening, we identified here the transcriptional corepressor CtBP-interacting protein (CtIP) as a SIAH-1-interacting protein. CtIP has been proposed as a regulator of p21(Waf-1/Cip-1) gene transcription through a protein complex involving BRCA1. We demonstrate that SIAH-1 associates with CtIP both in vitro and in vivo. This interaction led to CtIP degradation by the ubiquitin-proteasome pathway. As expected, SIAH-1 induced p21(Waf-1/Cip-1) transcription in Jurkat-T cell. Surprisingly, a SIAH protein deleted of its RING finger, SIAH-1DeltaN, which is able to interact with CtIP but does not promote its degradation, also induced transcription from the p21(Waf-1) promoter in a similar extent as did SIAH-1. Our results suggest that p21(Waf-1/Cip-1) induction by SIAH-1 could not be mediated by CtIP degradation.
Germani
Antonia
A
Laboratory of Vascular Biology and Gene Therapy, Centro Cardiologico Fondazione-IRCCS, Via Parea 4, 20138 Milano, Italy.
Prabel
Audrey
A
Mourah
Samia
S
Podgorniak
Marie-Pierre
MP
Di Carlo
Anna
A
Ehrlich
Ricardo
R
Gisselbrecht
Sylvie
S
Varin-Blank
Nadine
N
Calvo
Fabien
F
Bruzzoni-Giovanelli
Heriberto
H
D002352:Carrier Proteins / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004706:Endodeoxyribonucleases; D006801:Humans; D019169:Jurkat Cells; D009097:Multienzyme Complexes / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases; D000098563:Seven in Absentia Proteins
C493956:CDKN1A protein, human; D002352:Carrier Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D009097:Multienzyme Complexes; D009687:Nuclear Proteins; D011506:Proteins; D044767:Ubiquitin-Protein Ligases; D000098563:Seven in Absentia Proteins; D004706:Endodeoxyribonucleases; C410741:RBBP8 protein, human; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex