THE IMPORTANCE OF DOWNSTREAM DELTA-FACTOR BINDING-ELEMENTS FOR THE ACTIVITY OF THE RPL32 PROMOTER

A salient feature of mammalian ribosomal protein genes is the location of promoter elements downstream, as well as upstream, of the transcri ptional start point. Previous functional studies of the mouse rpL32 ge ne (Chung and Perry, Mol. Cell. Biol. 9, 2075; 1989) indicated that th e first intron of this gene contains such an element. We show here tha t this element encompasses a binding site for a zinc finger nuclear pr otein known as delta (YY-1, muE1, UCRBP). The intronic delta site (del ta(i)) is located 32 bp downstream of another delta site in the first exon (delta(e)). Transfection experiments with genes containing delete rious mutations in one or both delta sites or having alterations in th e spacing between the sites indicate that the two delta elements funct ion independently and contribute additively to the overall strength of the rpL32 promoter. Moreover, the contribution of the delta(i) elemen t is the same whether it is oriented parallel or antiparallel to the d elta(e) element. Together, the two delta elements raise the expression level about 10-fold over that attained by the upstream and initiator portions of the promoter. The positive role of the delta factor in rpL 32 expression contrasts strikingly with its repressive role in various other genes.