THE ARABIDOPSIS ADH GENE EXHIBITS DIVERSE NUCLEOSOME ARRANGEMENTS WITHIN A SMALL DNASE-I-SENSITIVE DOMAIN

The alcohol dehydrogenase (Adh) gene from Arabidopsis shows enhanced s ensitivity to DNase I in cells that express the gene. This generalized sensitivity to DNase I is demarcated by position -500 on the 5' side and the end of the mRNA on the 3' side. Thus, the gene defined as the promoter and mRNA coding region corresponds very closely in size with the gene defined as a nuclease-sensitive domain. This is a remarkably close correspondence between a sensitive domain and a eukaryotic trans criptional unit, because previously reported DNase I-sensitive domains include large regions of DNA that are not transcribed. Nucleosomes ar e present in the coding region of the Adh gene when it is expressed, i ndicating that the transcriptional elongation process causes nucleosom e disruption rather than release of nucleosomes from the coding region . In addition, the regulatory region contains a loosely positioned nuc leosome that is separated from adjacent nucleosomes by internucleosomi c DNA segments longer than the average linker DNA in bulk chromatin, T his specific array of nucleosomes coexists with bound transcription fa ctors that could contribute to the organization of the nucleosome arra ngement. These results enhance our understanding of the complex intera ctions among DNA, nucleosomes, and transcription factors during gene e xpression in plants.