Article

The Transcriptional Regulating Protein of 132 kDa (TReP-132) Enhances P450scc Gene Transcription through Interaction with Steroidogenic Factor-1 in Human Adrenal Cells

Oncology and Molecular Endocrinology Research Center, Laval University, Québec GIK 7P4, Canada.
Journal of Biological Chemistry (Impact Factor: 4.6). 11/2002; 277(42):39144-55. DOI: 10.1074/jbc.M205786200
Source: PubMed

ABSTRACT The human P450scc gene is regulated by the tissue-specific orphan nuclear receptor, steroidogenic factor-1 (SF-1), which plays a key role in several physiologic processes including steroid synthesis, adrenal and gonadal development, and sexual differentiation. Several studies have demonstrated the interaction of SF-1 with different proteins. However, it is clear that additional factors not yet identified are involved with SF-1 to regulate different target genes. Recently, it was demonstrated that a novel transcriptional regulating protein of 132 kDa (TReP-132) regulates expression of the human P450scc gene. The overexpression of TReP-132 in adrenal cells increases the production of pregnenolone, which is associated with the activation of P450scc gene expression. Considering the colocalization of TReP-132 and SF-1 in steroidogenic tissues such as the adrenal and testis, and the presence of two putative LXXLL motifs in TReP-132 that can potentially interact with SF-1, the relationship between these two factors on the P450scc gene promoter was determined. The coexpression of SF-1 and TReP-132 in adrenal NCI-H295 cells cooperates to increase promoter activity. Pull-down experiments demonstrated the interaction between TReP-132 and SF-1, and this was further confirmed in intact cells by coimmunoprecipitation/Western blot and two-hybrid analyses. Deletions and mutations of the TReP-132 cDNA sequence demonstrate that SF-1 interaction requires the LXXLL motif found at the amino-terminal region of the protein. Also, the "proximal activation domain" and the "AF-2 hexamer" motif of SF-1 are involved in interaction with TReP-132. Consistent with previous studies showing interaction between CBP/p300 and SF-1 or TReP-132, the coexpression of these three proteins results in a synergistic effect on P450scc gene promoter activity. Taken together the results in this study identify a novel function of TReP-132 as a partner in a complex with SF-1 and CBP/p300 to regulate gene transcription involved in steroidogenesis.

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    • "s shown in Fig. 3B, TdIF1 unexpectedly bound to truncated TReP-132 residues ranging from 387 to 444 without the LXXLL motif and did not bind to del7, suggesting that TdIF1 binds to a confined region from 387 to 407 of TReP-132. Recently, TReP-132 has been reported to bind to SF-1 only through its N-terminal LXXLL, not through its C-terminal LXXLL (Gizard et al . 2002b). Thus, we then examined the possibility of binding through the N-terminal LXXLL. As shown in Fig. 3B (del8), no binding through the N-terminal LXXLL was observed. We therefore conclude that TdIF1 mainly binds to the novel confined region between residues 387 and 407 in TReP-132."
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