Transcription factor binding and spacing constraints in the human β-actin proximal promoter

Abstract

The human β-actln promoter, Including its 5′ flanking region and 5′ untranslated region, is ubiquitously active in mammalian cells in culture. In this report we investigated the transcriptional activity of, and the proteirvDNA interactions that occur within, the proximal region of the human β-actin promoter. Efficient β-actin promoter activity in transfected human HeLa cells requires only 114bp of 5′ flanking sequences. Two of the cis-acting regulatory elements within this region of the β-actin promoter, the CCAAT box and proximal CCArGG box, are specific In vitro binding sites for the transcription factors, nuclear factor Y (NF-Y) and serum response factor (p67^SRF), respectively. These two elements are required together to stimulate in vivo transcription from the homologous as well as a heterologous promoter. Finally, a particular spatial alignment between the CCAAT box and proximal CCArGG box is required for trans-activation in vivo. The above provides strong evidence for a functional interaction between NF-Y and p67^SRF when bound to their respective binding sites in the β-actin promoter.