Differential expression of the adipocyte amino acid transporter is transactivated by SP1 and SP3 during the 3T3-L1 preadipocyte differentiation process

It was identified that a Spl-like cis-element in the adipocyte amino acid t ransporter gene (AAAT) promoter is the major cis-motif for its induced expr ession during the 3T3-L1 preadipocyte differentiation process. Electrophore tic mobility shift analysis of this cia DNA element showed that the transcr iption factors binding to this sequence were Sp1 and Sp3. Protein analysis of Sp1 and Sp3 in nuclear extracts from 3T3-L1 cells at various differentia tion stages indicated that these two transcription factors existed in nonin duced 3T3-L1 preadipocytes, but they did not bind to the AAAT promoter elem ent with high affinity. They were activated after differentiation induction . It was further demonstrated that dephosphorylation of Sp1 increased its b inding affinity to this inducible AAAT promoter element. (C) 2000 Academic Press.