Histone H1 and chromatin interactions in human fibroblast nuclei after H1 depletion and reconstitution with H1 subfractions.
BACKGROUND
Linker histones constitute a family of lysine-rich proteins associated with nucleosome core particles and linker DNA in eukaryotic chromatin. In permeabilized cells, they can be extracted from nuclei by using salt concentration in the range of 0.3 to 0.7 M. Although other nuclear proteins are also extracted at 0.7 M salt, the remaining nucleus represents a template that is relatively intact.


METHODS
A cytochemical method was used to study the affinity of reconstituted linker histones for chromatin in situ in cultured human fibroblasts. We also investigated their ability to condense chromatin by using DNA-specific osmium ammine staining for electron microscopy.


RESULTS
Permeabilized and H1-depleted fibroblast nuclei were suitable for the study of linker histone-chromatin interactions after reconstitution with purified linker histone subfractions. Our results showed that exogenous linker histones bind to chromatin with lower affinity than the native ones. We detected no significant differences between the main H1 and H1 degrees histone fractions with respect to their affinity for chromatin or in their ability to condense chromatin.


CONCLUSIONS
Linker histone interactions with chromatin are controlled also by mechanisms independent of linker histone subtype composition.
Kostova
Nora N
NN
Institute of Molecular Biology, Bulgarian Academy of Sciences, Sofia, Bulgaria.
Srebreva
Ljuba
L
Markov
Dimiter V
DV
Rundquist
Ingemar
I
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology*; D006657:Histones / Q000172:deficiency* / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D051379:Mice; D011485:Protein Binding
D002843:Chromatin; D006657:Histones; C024063:nuclear protein H1(0)