Expression, structure and evolution of H1 linker histones

Authors

  • Roger Vila
  • Pere Suau
  • Imma Ponte

Abstract

H1 linker histones bind to linker DNA and contribute to the stabilization of both the nucleosome and chromatin higherorder structure. We have studied aspects of the expression, structure and evolution of H1 linker histones. H1 presents multiple isoforms. In rat cerebral cortex neurons, the subtypes H1a,b,c,d are replaced, to varying degrees, by H1e during postnatal development. In vivo labelling experiments have shown the importance of differential turnover and synthesis rates in defining the H1a-e subtype composition of chromatin. H1o is regulated in a different way, its expression being linked to neuronal terminal differentiation; it is also the only histone subtype which is regulated by external signals in specific neuronal populations. We estimated the rates of nucleotide substitution for several H1 subtypes. The rates of nonsynonymous substitution differed among subtypes by almost one order of magnitude. Such a wide variation in the tolerance of amino acid substitutions is consistent with the functional differentiation of the subtypes. We showed, using CD, 1H-NMR and IR spectroscopy, that the H1 terminal domains acquire substantial amounts of secondary structure upon interaction with DNA. In H1o, we characterized an ahelical element in the N-terminal domain and a helix-turn motif in the C-terminal domain, both adjacent to the globular domain. The N-terminal domain of H1e contains two !-helices separated by a Gly-Gly motif, which behaves as a flexible linker.

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Published

2003-08-01

Issue

Section

Research reviews