CLONING AND TRANSCRIPTIONAL REGULATION OF A NOVEL ADIPOCYTE-SPECIFIC GENE, FSP27 - CAAT-ENHANCER-BINDING PROTEIN (C EBP) AND C/EBP-LIKE PROTEINS INTERACT WITH SEQUENCES REQUIRED FOR DIFFERENTIATION-DEPENDENT EXPRESSION/

We have reported previously the cloning of several cDNAs whose mRNAs a re induced during differentiation of the adipogenic cell line TA1. Her e we characterize an adipocyte-specific gene, which we refer to as FSP 27 (formerly clone 47), that encodes a protein of 27 kDa, the sequence of which is unrelated to any in the current data banks. The FSP27 pro moter confers adipocyte-specific expression to a heterologous reporter gene in transfected adipogenic cell lines, e.g. TA1 and 3T3-L1. Analy sis of regulatory elements in the FSP27 promoter region indicates the presence of (a) a proximal palindromic sequence that is necessary for adipocyte-specific expression; and (b) a distal differentiation-indepe ndent enhancer-like element. The palindromic sequence TTCGAAA is prote cted from digestion by DNase I using nuclear extracts from TA1 preadip ocytes and adipocytes. Heated rat liver nuclear extract, a very abunda nt source of the transcription factor CAAT-enhancer-binding protein (C /EBP) and related proteins, generates an equivalent footprint over the palindrome. However, C/EBP can account for only a portion of the prot ein-DNA complexes in TA1 cells because preadipocytes as well as adipoc ytes contain proteins distinct from C/EBP which interact with the same sequence. We suggest that C/EBP and other C/EBP-like proteins play a critical role in regulating the transcription of the fat-specific gene FSP27.