Matrix attachment region-dependent function of the immunoglobulin mu enhancer involves histone acetylation at a distance without changes in enhancer occupancy.
Nuclear matrix attachment regions (MARs), which flank the immunoglobulin mu heavy-chain enhancer on either side, are required for the activation of the distal variable-region (V(H)) promoter in transgenic mice. Previously, we have shown that the MARs extend a local domain of chromatin accessibility at the mu enhancer to more distal sites. In this report, we examine the influence of MARs on the formation of a nucleoprotein complex at the enhancer and on the acetylation of histones, which have both been implicated in contributing to chromatin accessibility. By in vivo footprint analysis of transgenic mu gene constructs, we show that the occupancy of factor-binding sites at the mu enhancer is similar in transcriptionally active wild-type and transcriptionally inactive DeltaMAR genes. Chromatin immunoprecipitation experiments indicate, however, that the acetylation of histones at enhancer-distal nucleosomes is enhanced 10-fold in the presence of MARs, whereas the levels of histone acetylation at enhancer-proximal nucleosomes are similar for wild-type and DeltaMAR genes. Taken together, these data indicate that the function of MARs in mediating long-range chromatin accessibility and transcriptional activation of the V(H) promoter involves the generation of an extended domain of histone acetylation, independent of changes in the occupancy of the mu enhancer.
Fernández
L A
LA
Howard Hughes Medical Institute and Department of Microbiology and Immunology, University of California, San Francisco, California 94143, USA.
Winkler
M
M
Grosschedl
R
R
D000107:Acetylation; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018983:DNA Footprinting; D003850:Deoxyribonuclease I / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D005803:Genes, Immunoglobulin / Q000235:genetics*; D006657:Histones / Q000737:chemistry / Q000378:metabolism*; D007148:Immunoglobulin mu-Chains / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D015530:Nuclear Matrix / Q000378:metabolism*; D009707:Nucleosomes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D017384:Sequence Deletion; D019076:Transgenes / Q000235:genetics
D006657:Histones; D007148:Immunoglobulin mu-Chains; D009707:Nucleosomes; D004247:DNA; D003850:Deoxyribonuclease I