title: SSRP1 functions as a co-activator of the transcriptional activator p63.
abstract: The p53 homolog p63 is a transcriptional activator. Here, we describe the identification of an HMG1-like protein SSRP1 as a co-activator of p63. Over expression of wild-type, but not deletion mutant, SSRP1 remarkably enhanced p63gamma-dependent luciferase activity, G1 arrest, apoptosis and expression of endogenous PIG3, p21(Waf1/cip1) and MDM2 in human p53-deficient lung carcinoma H1299 cells and mouse embryonic fibroblasts. Also, SSRP1 interacted to p63gamma in vitro and in cells, and resided with p63gamma at the p53-responsive DNA element sites of the cellular endogenous MDM2 and p21(Waf1/cip1) promoters. Moreover, N-terminus-deleted p63 (DeltaN-p63) bound to neither SSRP1 nor its central domain in vitro. Accordingly, SSRP1 was unable to stimulate DeltaN-p63-mediated residual luciferase activity and apoptosis in cells. Finally, the ectopic expression of the central p63-binding domain of SSRP1 inhibited p63-dependent transcription in cells. Thus, these results suggest that SSRP1 stimulates p63 activity by associating with this activator at the promoter.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97201, USA.
authors.forename: Shelya X
authors.initials: SX
authors.lastname: Zeng
authors.forename: Mu-Shui
authors.initials: MS
authors.lastname: Dai
authors.forename: David M
authors.initials: DM
authors.lastname: Keller
authors.forename: Hua
authors.initials: H
authors.lastname: Lu
mesh_terms: D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D002460:Cell Line; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016193:G1 Phase; D017353:Gene Deletion; D016147:Genes, Tumor Suppressor; D006609:High Mobility Group Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008156:Luciferases / Q000235:genetics; D008565:Membrane Proteins; D051379:Mice; D009687:Nuclear Proteins; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000235:genetics; D051736:Proto-Oncogene Proteins c-mdm2; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins
chemical_list: C493956:CDKN1A protein, human; C081876:CKAP4 protein, human; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; C073537:SSRP1 protein, human; C115051:TP63 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; C486419:Trp63 protein, mouse; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C070454:Ssrp1 protein, mouse; D008156:Luciferases; C497206:MDM2 protein, human; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2