Histone H2AZ dimerizes with a novel variant H2B and is enriched at repetitive DNA in Trypanosoma brucei.
H2AZ is a widely conserved histone variant that is implicated in protecting euchromatin from the spread of heterochromatin. H2AZ is incorporated into nucleosomes as a heterodimer with H2B, by the SWR1 ATP-dependent chromatin-remodeling complex. We have identified a homolog of H2AZ in the protozoan parasite Trypanosoma brucei, along with a novel variant of histone H2B (H2BV) that shares approximately 38% sequence identity with major H2B. Both H2AZ and H2BV are essential for viability. H2AZ localizes within the nucleus in a pattern that is distinct from canonical H2A and is largely absent from sites of transcription visualized by incorporation of 5-bromo-UTP (BrUTP). H2AZ and H2BV colocalize throughout the cell cycle and exhibit nearly identical genomic distribution patterns, as assessed by chromatin immunoprecipitation. H2AZ co-immunoprecipitates with H2BV but not with histones H2B or H2A nor with the variant H3V. These data strongly suggest that H2AZ and H2BV function together within a single nucleosome, marking the first time an H2AZ has been shown to associate with a non-canonical histone H2B.
Lowell
Joanna E
JE
Laboratory of Molecular Parasitology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Kaiser
Franziska
F
Janzen
Christian J
CJ
Cross
George A M
GA
D000818:Animals; D042002:Chromatin Assembly and Disassembly / Q000502:physiology*; D047369:Chromatin Immunoprecipitation / Q000379:methods; D016054:DNA, Protozoan / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D022041:Euchromatin / Q000235:genetics / Q000378:metabolism; D006657:Histones; D020071:Interspersed Repetitive Sequences / Q000502:physiology*; D009707:Nucleosomes / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000166:cytology / Q000235:genetics / Q000378:metabolism*
D016054:DNA, Protozoan; D022041:Euchromatin; D006657:Histones; D009707:Nucleosomes; D015800:Protozoan Proteins