MOLECULAR-STRUCTURE AND FUNCTION OF RAT CCAAT-ENHANCER BINDING PROTEIN-DELTA GENE PROMOTER

CCAAT-enhancer binding protein-delta (C/EBP delta) is a transcriptiona l nuclear factor, and belongs to basic region-leucine zipper class DNA binding proteins. One genomic clone containing a 12-kb sequence of th e C/EBP delta gene was isolated from a rat genomic library, and a 2,05 6-bp fragment containing the 5'-flanking region was characterized. Seq uence analysis of this fragment revealed that there were a TATA-like s equence (TAGAAAA) and many transcriptional regulatory elements. The tr anscription start site of the gene was determined by both primer exten sion analysis and riboprobe mapping. Both analyses indicated that tile transcription start site was located at 31-bp downstream of the TATA- like sequence. Transient transfection experiments showed that the frag ment cloned in this study was able to act as a functional promoter in rat vascular smooth muscle cells. The 5'-deletion analysis of this fra gment revealed that the sequence spanning -235 through -82, which was designated as an upstream control element (UCE), remarkably increased a basal promoter activity of the C/EBP delta gene, and was also able t o act as a promoter by itself. in addition, we also studied effects of the UCE on the heterologous gene promoter including rat alpha-actin g ene promoter or SV40 virus promoter. Interestingly, the UCE specifical ly increased the promoter activity of the rat alpha-actin gene suggest ing that the C/EBP delta gene may be positively controlled by the UCE via a cell-type or promoter-type specific manner. (C) 1997 Academic Pr ess.