A positioned nucleosome on the human U6 promoter allows recruitment of SNAPc by the Oct-1 POU domain

The human snRNA promoters contain a proximal sequence element (PSE) required for basal transcription and a distal sequence element (DSE) required for activated transcription. The PSE recruits the multisubunit factor SNAPc, whereas the DSE recruits Oct-1. Oct-1 and SNAPc bind cooperatively to DNA when their respective binding sites are moved into proximity through a mechanism that involves a defined protein-protein contact. Here, we show that on the natural U6 promoter, cooperative binding of Oct-1 and SNAPc is mediated by a positioned nucleosome that resides between the DSE and the PSE. This cooperative binding requires the same protein-protein contact as cooperative binding to closely spaced sites on naked DNA and mediates transcription activation.