DNA methylation: correlation with DNase I sensitivity of chicken ovalbumin and conalbumin chromatin

Abstract

To analyse the relationship between DNA undermethylation at some sites in the ovalbumin and conalbumin gene regions (1) and the expression of these genes in chick oviduct, digestions with HhaI, which differentiates between methylated and unmethylated HhaI restriction sites, was performed on DNA isolated from chicken erythrocyte or oviduct chromatin treated with DNase I which degrades preferentially "active" chromatin. This was followed by analysis with ovalbumin- and conalbumin-specific hybridization probes. We conclude that the residual DNA methylation found at some sites of the ovalbumin and conalbumin gene regions is derived from the fraction of cells in which the chromatin of these genes is not in an "active" form. On the other hand, the ovalbumin and conalbumin sites which are partially unmethylated in erythrocyte DNA correspond to chromatin regions which are not DNase I-senitive. We have also detected a site about 1 kb downstream from the 3' end of the conalbumin gene that is hypersensitive to DNase I in all tissues tested.

Disruption of the typical chromatin structure in a 2500 base-pair region at the 5′ end of the actively transcribed ovalbumin gene.

“…However, we cannot formally exclude a multiphasic distribution of nucleosomes, but the number of distinct phases must be high. The disappearance of cleavage site F and the concomittant appearance of site G occurs both in erythrocyte and oviduct chromatins (see below); these alterations suggest that, irrespective of the (0) activity of the ovalbumin gene, some "structural" protein(s) could be bound to this region of the chicken genome in both erythrocyte and oviduct cells, protecting cleavage site F and "inducing" the new site G. Absence of a "normal" nucleosomal pattern in the S '-end flanking region of the active ovalbumin gene in laying hen oviduct Ovalbumin gene chromatin is preferentially digested by DNase I and micrococcal nuclease when the gene is expressed (Bellard et al, 1977(Bellard et al, , 1980Bloom and Anderson, 1979;Garel and Axel, 1976;Kuo et al, 1979;Lawson et al, 1980;Senear and Palmiter, 1981). These modifications extend on both sides of this gene (Bellard et al, 1980;Lawson et al, 1980).…”

5-Methylcytosine depletion during tumour development: An extension of the miscoding concept

“…demonstrated the existence of a class of methylation sites (mvar) within and around the conalbumin, ovomucoid, and ,B-globin genes, the variable methylation of which correlated with transcriptional activity. When a gene region is in an active chromatin conformation, as measured by DNase I sensitivity (Kuo et al, 1979), there is extensive hypomethylation at many of these mvar sites. Sites of residual methylation near transcribed genes, as well as undermethylated sites near genes not being transcribed, were absent in DNase Isensitive active chromatin.…”

DNA Methylation--A Regulatory Signal in Eukaryotic Gene Expression

“…In particular, tissue-specific differences in methylation patterns have been observed (Vanyushin et al, 1973), namely for the globin gene (Waalwijk & FlaveU, 1978 b;McGhee & Ginder, 1979;, for chicken ovalbumin (Mandel & Chambon, 1979;Kuo et al, 1979) and for a variety of genes in the sea urchin Echinus esculentus (Bird et al, 1979). In most cases, undermethylated genes have been observed to be more actively expressed.…”