Interactions between XIAP associated factor 1 and a nuclear co-activator, CBP, in colon cancer cells.
OBJECTIVE
XIAP-associated factor 1 (XAF1) is a nuclear protein. CBP, the cAMP response element binding protein (CREB)-binding protein, plays an important role as a multifunctional transcriptional co-activator. In this investigation, we aimed to study the putative interaction between XAF1 and CBP in colon cancer cells.


METHODS
Expressions of XAF1 and CBP were detected by Western blot and RT-PCR. The interaction between XAF1 and CBP was investigated by the glutathione S-transferase (GST) pull-down assay, colocalization and co-immunoprecipitation analysis. Cell proliferation was examined by cell number counting.


RESULTS
Both XAF1 and CBP were co-localized in the nuclei of colon cancer cells and they demonstrated a physical interaction, as revealed by GST pull-down assay and co-immunoprecipitation analysis. CBP I peptide (residues 1-1098) was the interacting domain for XAF1 binding. The functional implication of the interaction between XAF1 and CBP was demonstrated by the finding that cell growth inhibition by XAF1 was potentiated by cotransfection with CBP. Furthermore, a reporter assay demonstrated that cotransfection with XAF1 and CBP led to marked reduction in phorbol ester 12-O-tetradecanoylphorbol-13-acetate (PMA)-stimulated adaptor-related protein complex 1 activity.


CONCLUSIONS
CBP is a novel binding partner of XAF1, and the interaction between XAF1 and CBP and their functional consequence were mediated by adaptor-related protein complex 1.
Sun
Yunwei
Y
Division of Gastroenterology, Ruijin Hospital, Department of Medicine, Shanghai Jiaotong University, Shanghai, PR China.
Qiao
Liang
L
Zou
Bing
B
Xia
Harry Hua-Xiang
HH
Gu
Qing
Q
Ma
Juan
J
Lin
Marie C M
MC
Zhu
Qi
Q
Zhu
Senlin
S
Dai
Yun
Y
Wong
Benjamin C Y
BC
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D050882:CREB-Binding Protein / Q000235:genetics / Q000378:metabolism*; D002277:Carcinoma / Q000378:metabolism*; D049109:Cell Proliferation; D003110:Colonic Neoplasms / Q000378:metabolism*; D015870:Gene Expression; D005982:Glutathione Transferase; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D050880:p300-CBP Transcription Factors / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; C417551:XAF1 protein, human; D050882:CREB-Binding Protein; D050880:p300-CBP Transcription Factors; D005982:Glutathione Transferase