Activation of the chicken Ig-beta locus by the collaboration of scattered regulatory regions through changes in chromatin structure.

A total of 10 B-lymphocyte-specific DNase I hypersensitive sites located in the chicken Ig-beta locus were divided into four regions and combinations of deletions of these regions were carried out. A decrease in transcription of the Ig-beta gene to <3% was demonstrated in cells with deletions in all four regions. The Ig-beta chromatin was resistant to DNase I digestion in these cells. Thus, the collaboration is shown to convert the Ig-beta chromatin from the condensed state to a relaxed state. H3 and H4 acetylation decreased to <8% but H3K4 hypermethylation was observed at the Ig-beta promoter and exon 3. The collaboration of four regions had virtually no effect on CG hypomethylation in the region upstream the transcriptional start site. Accordingly, neither the DNase I general sensitive state in the Ig-beta chromatin nor hyperacetylation of H3 and H4 histones in the promoter proximal region causes H3K4 di-methylation or CG hypomethylation in the promoter. From these analyses, a chromatin situation was found in which both an active state, such as enhanced H3K4 methylation, or CG hypomethylation, and an inactive state, such as DNase I resistance in the Ig-beta chromatin or hypoacetylation of H3 and H4 histones in the Ig-beta locus, coexist.