Chromatin: Nucleosome Positioning – the GAL Promoter

The yeast GAL1–10 genes provide an attractive system for examining nucleosome structure–function relationships, due to their tight regulation and ability to be studied in single copy using combined genetic/biochemical approaches. The GAL1–10 promoter possesses a functionally distinctive chromatin organization. The major promoter elements (the gene-specific upstream activation sequences (UAS G )), which are the binding sites for the major activator (Gal4p), reside in a constitutively nucleosome-free domain. Positioned nucleosomes cover the surrounding regions, including the TATA and transcription start sites, when the genes are inactive. These nucleosomes are completely disrupted during gene activity. Moreover, promoter nucleosome-regulatory factor interplay is a major aspect of GAL1–10 gene regulation.