Pax5 and Linker Histone H1 Coordinate DNA Methylation and Histone Modifications in the 3′ Regulatory Region of the Immunoglobulin Heavy Chain Locus

Abstract

The 3′ regulatory region (3′ RR) of the murine immunoglobulin heavy chain (IgH) locus contains multiple DNase I-hypersensitive (hs) sites. Proximal sites hs3A, hs1.2, and hs3B are located in an extensive palindromic region and together with hs4 are associated with enhancers involved in the expression and class switch recombination of IgH genes. Distal hs5, -6, and -7 sites located downstream of hs4 comprise a potential insulator for the IgH locus. In pro-B cells, hs4 to -7 are associated with marks of active chromatin, while hs3A, hs1.2, and hs3B are not. Our analysis of DNA methylation-sensitive restriction sites of the 3′ RR has revealed a similar modular pattern in pro-B cells; hs4 to -7 sites are unmethylated, while the palindromic region is methylated. This modular pattern of DNA methylation and histone modifications appears to be determined by at least two factors: the B-cell-specific transcription factor Pax5 and linker histone H1. In pre-B cells, a region beginning downstream of hs4 and extending into hs5 showed evidence of allele-specific demethylation associated with the expressed heavy chain allele. Palindromic enhancers become demethylated later in B-cell differentiation, in B and plasma cells.

SUPPLEMENTAL MATERIAL

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ACKNOWLEDGMENTS

This work was supported by the AECOM Cancer Center (grant P30CA1330) and by NIH grants AI13509 (to B.K.B.) and AI026782 (to R.R.H.) from the National Institute of Allergy and Infectious Diseases.

The content of this paper is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Allergy and Infectious Diseases or the National Institutes of Health.

We thank Francine Garrett and Nasrin Ashouian for initial studies of DNA methylation of the 3′ RR, Vincent Yue for help in preparing figures, and Meinrad Busslinger for Pax5^−/− pro-B cells.