Effects of H1 Histone Variant Overexpression on Chromatin Structure*

By A. Gunjan, B. Alexander, D. Sittman, David T Brown. 1999

The importance of histone H1 heterogeneity and total H1 stoichiometry in chromatin has been enigmatic. Here we report a detailed characterization of the chromatin structure of cells overexpressing either H10 or H1c. Nucleosome spacing was found to change during cell cycle progression, and overexpression of either variant in exponentially growing cells results in a 15-base pair increase in nucleosome repeat length. H1 histones can also assemble on chromatin and influence nucleosome spacing in the absence of DNA replication. Overexpression of H10 and, to a lesser extent, H1c results in a decreased rate of digestion of chromatin by micrococcal nuclease. Using green fluorescent protein-tagged H1 variants, we show that micrococcal nuclease-resistant chromatin is specifically enriched in the H10 variant. Overexpression of H10 results in the appearance of a unique mononucleosome species of higher mobility on nucleoprotein gels. Domain switch mutagenesis revealed that either the N-terminal tail or the central globular domain of the H10 protein could independently give rise to this unique mononucleosome species. These results in part explain the differential effects of H10 and H1c in regulating chromatin structure and function.

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Citations in the corpus

Dynamic binding of histone H1 to chromatin in living cells (2000, methodology): “We established stable cell lines in mouse BALB/c 3T3 fibroblasts as describe”