NUCLEOSOME POSITIONING PROPERTIES OF THE ALBUMIN TRANSCRIPTIONAL ENHANCER

Considering the importance of nucleosome position with regard to how r egulatory factors recognize their binding sites in chromatin, we have investigated the inherent nucleosome positioning properties of a trans criptional enhancer of the albumin gene. In the liver, where the album in gene is highly expressed, the enhancer exists in an array of precis ely positioned, nucleosome-like particles with transcription factors b ound. In the absence of specific binding factors, such as in non-liver tissues or in polynucleosome arrays assembled in vitro, nucleosomes a re randomly positioned over the enhancer, Herein we investigate the in trinsic nucleosome positioning properties of the central enhancer sequ ence assembled into mononucleosome core particles in vitro. We find th at the enhancer DNA prefers three translational positions, each of whi ch utilizes different rotational settings on the nucleosome core. We c onclude that DNA binding factors that position nucleosomes may do so b y stabilizing one configuration out of several that can be adopted by the underlying DNA, and that the potential exists for different positi ons to be stabilized at different stages of development.