The importance of downstream δ-factor binding elements for the activity of the rpL32 promoter

Abstract

A salient feature of mammalian ribosomal protein genes Is the location of promoter elements downstream, as well as upstream, of the transcrlptlonal start point. Previous functional studies of the mouse rpL32 gene (Chung and Perry, Mol. Cell. Blol. 9, 2075; 1989) Indicated that the first Intron of this gene contains such an element. We show here that this element encompasses a binding site for a zinc finger nuclear protein known as δ (YY-1, μE1, UCRBP). The Intronlc δ site (δ1) Is located 32 bp downstream of another δ site In the first exon (δe). Transfectlon experiments with genes containing deleterious mutations In one or both δ sites or having alterations In the spacing between the sites indicate that the two δ elements function Independently and contribute additlvely to the overall strength of the rpL32 promoter. Moreover, the contribution of the δ1 element is the same whether It is oriented parallel or antiparallel to the δe element. Together, the two δ 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 δ factor in rpL32 expression contrasts strikingly with Its repressive role in various other genes. © 1993 Oxford University Press.