Weak but Uniform Enrichment of the Histone Variant macroH2A1 along the Inactive X Chromosome

Abstract

We studied the enrichment and distribution of the histone variant mH2A1 in the condensed inactive X (Xi) chromosome. By using highly specific antibodies against mH2A1 and stable HEK 293 cell lines expressing either green fluorescent protein (GFP)-mH2A1 or GFP-H2A, we found that the Xi chromosome contains ∼1.5-fold more mH2A1 than the autosomes. To determine the in vivo distribution of mH2A1 along the X chromosome, we used a native chromatin immunoprecipitation-on-chip technique. DNA isolated from mH2A1-immunoprecipitated nucleosomes from either male or female mouse liver were hybridized to tiling microarrays covering 5 kb around most promoters or the entire X chromosome. The data show that mH2A1 is uniformly distributed across the entire Xi chromosome. Interestingly, a stronger mH2A1 enrichment along the pseudoautosomal X chromosome region was observed in both sexes. Our results indicate a potential role for macroH2A in large-scale chromosome structure and genome stability.

ACKNOWLEDGMENTS

This work was supported by INSERM, CNRS, and ANR project no. NT05-1_41978 and by the GEN-AU initiative of the Austrian Ministry of Science.

S.D. acknowledges La Ligue Nationale contre le Cancer (Equipe labelisée La Ligue). We thank H. Fiegler and N. P. Carter for help in the initial stage of this work.