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H2A.Z marks the 5′ ends of both active and inactive genes in euchromatin
Author(s) -
Madhani Hiten
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a466-b
Subject(s) - euchromatin , nucleosome , histone octamer , biology , histone , genetics , histone methylation , chromatin , histone h2a , histone code , gene , microbiology and biotechnology , heterochromatin , dna methylation , gene expression
In S. cerevisiae, histone variant H2A.Z is deposited in euchromatin at the flanks of silent heterochromatin to prevent its ectopic spread. The degree to which H2A.Z is found and functions elsewhere is unknown. Here we show that H2A.Z nucleosomes are found at promoter regions of nearly all genes in euchromatin. They generally occur as two positioned nucleosomes that flank a nucleosome‐free region (NFR) that contains the transcription start site. Astonishingly, enrichment at 5′ ends is independent of transcriptional state as it is observed not only at actively transcribed genes, but also at inactive loci. Mutagenesis of a typical promoter revealed a 22 bp segment of DNA sufficient to program formation of a NFR flanked by two H2A.Z nucleosomes. This segment contains a binding site of the Myb‐related protein Reb1 and an adjacent dT:dA tract. Efficient deposition of H2A.Z is further promoted by a specific pattern of histone H3 and H4 tail acetylation and the bromodomain protein Bdf1, a component of the Swr1 complex that deposits H2A.Z. These data define DNA‐ and histone‐based mechanisms by which dividing cells define the 5′ ends of genes and preserve their euchromatic state in the absence of transcription.