DNase I sensitivity of the chromatin of the yeast SUC2 gene for invertase.

The DNase I sensitivity of chromatin of the yeast SUC2 gene, which encodes two forms of invertase, has been studied both in the genome and in a multicopy plasmid carrying the gene and its flaking sequences. Whereas little if any difference in the DNase I sensitivity of the flanking regions was found between the repressed and the derepressed states, derepression of the gene was accompanied by a large increase in the sensitivity of the transcribed region. A well-defined DNase I hypersensitive site was found centered at approximately 120 bp downstream from the end of the coding region. This site seems to be flanked in the 3' non-coding region by strictly positioned nucleosomes, and the structure of this region changes upon derepression. In the 5' non-coding region two DNase I hypersensitive sites have been found flanking the TATA box and a set of three closely spaced hypersensitive sites occurs in an upstream regulatory sequence. The structure of these latter sites depends on the on-off state of transcription.