IDENTIFICATION OF A NOVEL REGULATORY ELEMENT IN THE C-MOS LOCUS THAT ACTIVATES TRANSCRIPTION IN SOMATIC-CELLS

We have identified a DNA sequence in the 5' flanking sequence of rat c -mos gene which fulfills operational criteria for enhancers, increasin g transcription from heterologous promoters in somatic cells. This new enhancer region contains some specific motifs such as two CArG boxes, two M-CAT binding sites and CCAAT consensus sequences. This Upstream Enhancer region (UER) is recognized by distinct protein complexes and particularly CArG2 and M-CAT R1 motifs, which are adjacent in the DNA sequence. Several lines of evidence indicate that none of the two CArG boxes bind to the Serum response factor (SRF). Site-directed mutation s of both the CArG2 and M-CAT R1 binding sites suppress their enhancer activity. These results suggest that direct and indirect interactions involving multiple nuclear factors and distinct elements of the UER m ay be required for its enhancer functions in somatic cells. (C) 1995 A cademic Press, Inc.