Histone variants, nucleosome assembly and epigenetic inheritance

Template copying is the basis for inheritance and specification of genetic information and for the propagation of DNA methylation. However, no templating machinery has been identified that is capable of propagating histone modifications and conformations. Potential solutions to this enigma come from...

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Bibliographic Details
Published in:Trends in genetics 2004-07, Vol.20 (7), p.320-326
Main Authors: Henikoff, Steven, Furuyama, Takehito, Ahmad, Kami
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Chromatin - genetics
Epigenesis, Genetic
Fundamental and applied biological sciences. Psychology
Genetic Variation
Genetics of eukaryotes. Biological and molecular evolution
Histones - chemistry
Histones - genetics
Histones - metabolism
Humans
Models, Molecular
Molecular and cellular biology
Nucleosomes - metabolism
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Summary:Template copying is the basis for inheritance and specification of genetic information and for the propagation of DNA methylation. However, no templating machinery has been identified that is capable of propagating histone modifications and conformations. Potential solutions to this enigma come from recent insights into histone variants and the specialized complexes that assemble them into nucleosomes. Different variants have been found to distinguish alternative chromatin states at centromeres, at the inactive mammalian X chromosome and at transcriptionally active loci. Remarkably, the histone variants H2A.Z and H3.3 have been found to participate in distinct nucleosome-assembly pathways, where H2A.Z is deposited specifically by the SWR1 complex, and H3.3 by the HIRA complex. For each of these pathways, the unit of assembly is a heterodimeric pair, which implies stepwise replacement of the nucleosomal octamer during transcription. The resulting replacement of modified histone variants might modulate barriers to transcription and perpetuate active chromatin states.
ISSN:0168-9525
DOI:10.1016/j.tig.2004.05.004