XXXX immunoglobulin kappa gene enhancer: chromatin structure analysis at high resolution.

@entity1 @entity19 @entity95 @entity2774 @entity9828 @entity28036
The @entity19 immunoglobulin kappa gene enhancer has previously been found to coincide with a region of altered chromatin structure reflected in a @entity9828 hypersensitivity site detectable on Southern blots of B-cell DNA. We examined the chromatin structure of the homologous region of @entity1 DNA using the high-resolution electroblotting method originally developed for genomic sequence analysis by G. Church and W. Gilbert (Proc. Natl. Acad. Sci. USA 81:1991-1995, 1984). Analysis of DNA isolated from cells treated in vivo with @entity28036 revealed two B-cell-specific sites of enhanced @entity2774 methylation. Both sites are located within perfect inverted repeats theoretically capable of forming cruciform structures; one of these repeats overlaps an enhancer core sequence. No enhancement or protection of @entity2774 methylation was observed within sequences similar to sites of altered methylation previously described in the immunoglobulin heavy-chain enhancer. Treatment of isolated nuclei with @entity9828 or a variety of restriction endonucleases defined a B-cell-specific approximately 0.25-kilobase region of enhanced nuclease susceptibility similar to that observed in the @entity19 kappa enhancer. The 130-base-pair DNA segment that shows high sequence conservation between @entity1 , @entity19 , and @entity95 DNAs lies at the 5' end of the nuclease-susceptible region.
