title: Isolation and characterization of PBP, a protein that interacts with peroxisome proliferator-activated receptor.
abstract: In an attempt to identify cofactors that could possibly influence the transcriptional activity of peroxisome proliferator-activated receptors (PPARs), we used a yeast two-hybrid system with Gal4-PPARgamma as bait to screen a mouse liver cDNA library and have identified steroid receptor coactivator-1 (SRC-1) as a PPAR transcriptional coactivator. We now report the isolation of a cDNA encoding a 165-kDa PPARgamma-binding protein, designated PBP which also serves as a coactivator. PBP also binds to PPARalpha, RARalpha, RXR, and TRbeta1, and this binding is increased in the presence of specific ligands. Deletion of the last 12 amino acids from the carboxyl terminus of PPARgamma results in the abolition of interaction between PBP and PPARgamma. PBP modestly increased the transcriptional activity of PPARgamma, and a truncated form of PBP (amino acids 487-735) acted as a dominant-negative repressor, suggesting that PBP is a genuine coactivator for PPAR. In addition, PBP contains two LXXLL signature motifs considered necessary and sufficient for the binding of several coactivators to nuclear receptors. In situ hybridization and Northern analysis showed that PBP is expressed in many tissues of adult mice, including the germinal epithelium of testis, where it appeared most abundant, and during ontogeny, suggesting a possible role for this cofactor in cellular proliferation and differentiation.
authors.affiliation: Department of Pathology, Northwestern University Medical School, Chicago, Illinois 60611, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhu
authors.forename: C
authors.initials: C
authors.lastname: Qi
authors.forename: S
authors.initials: S
authors.lastname: Jain
authors.forename: M S
authors.initials: MS
authors.lastname: Rao
authors.forename: J K
authors.initials: JK
authors.lastname: Reddy
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D018076:DNA, Complementary / Q000302:isolation & purification; D004268:DNA-Binding Proteins / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D017403:In Situ Hybridization; D008297:Male; D056913:Mediator Complex Subunit 1; D051379:Mice; D008969:Molecular Sequence Data; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D000077154:Rosiglitazone; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D013737:Testis / Q000737:chemistry; D013844:Thiazoles / Q000378:metabolism; D045162:Thiazolidinediones; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; C538856:Med1 protein, mouse; D056913:Mediator Complex Subunit 1; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D013844:Thiazoles; D045162:Thiazolidinediones; D014157:Transcription Factors; D000077154:Rosiglitazone