A novel core promoter element induces bidirectional transcription in CpG island

Abstract

How TATA-less promoters such as those within CpG islands (CGI) control gene expression is still a subject of active research. Here, we have identified the \"CGCG element\", a ten-base pair motif with a consensus sequence of TCTCGCGAGA present in a group of promoter-associated CGIs of ribosomal protein and housekeeping genes. This element is evolutionarily conserved in vertebrates, found in DNase-accessible regions and employs RNA polymerase 2 to activate gene expression. Through extensive analysis of several endogenous promoters, we demonstrate that this element activates bidirectional transcription through divergent start sites. Methylation of this element abrogates the associated promoter activity. When coincident with a TATA-box directional transcription remains CGCG-dependent. Because the CGCG element is sufficient to drive transcription, we propose that its unmethylated form functions as a core promoter of TATA-less CGI-associated promoters.