The arrangement of H5 molecules in extended and condensed chicken erythrocyte chromatin.

Abstract

Chemical cross‐linking with dithiobis(succinimidyl propionate) has been used to investigate the relative disposition of neighbouring H5 (H1) molecules in chicken erythrocyte chromatin in the extended (nucleosome filament) and condensed (300 A filament) states; in this chromatin H5 and H1 are interspersed along the nucleosome filament, rather than segregated into blocks, as shown by the nature of the cross‐linked dimers and their relative amounts. Detailed analysis of the cross‐linked H5 homopolymers from extended chromatin and condensed nuclear chromatin indicates which domains of H5 are in contact (or close proximity) in the two states. Two results suggest a polar, head‐to‐tail arrangement of H5 molecules along the nucleosome filament. This arrangement persists when chromatin adopts higher‐order structure but in the folded state neighbouring basic C‐terminal domains, in particular, are more closely juxtaposed than they are in extended chromatin.

Age‐related analysis of EcoRI generated satellite DNA‐containing chromatin of rat liver

“…4B). Whatever may be the cause of this increase, it possibly leads to the condensation of satellite DNA with Because HI plays a fundamental role in the formation of 30 nm fiber [22] and thus in the condensation of chromatin [3,23,24] and H i ° is probably associated with the loss of cell division capacity [25], their increase in old age is of great si~odficance. Cole [26] …”

A model for chromatin opening: stimulation of topoisomerase II and restriction enzyme cleavage of chromatin by distamycin.

“…Removal of histone HI would be synergistically beneficial for cleavage, due to the general unfolding of the chromatin fiber as well as steric de-blocking A model for a chromatin opening switch The chromatin fiber is thought to be stabilized by cooperatively interacting histone HI molecules, presumably via head-to-tail interactions (Thomas and Khabaza, 1980;Lennard and Thomas, 1985). In such a histone HI homopolymer, the DNA-bound members facilitate, via cooperative protein-protein interactions, the binding of adjacent members.…”

“…Interference with the binding of the repressor to OR, by mutation (we use the competitive inhibitor distamycin) results in a strongly reduced occupancy of the OR2 (Ptashne, 1986). Tazi and Bird, 1990) with histone HI molecules assembled in a polar head-to-tail fashion (Lennard and Thomas, 1985). A subfraction of histone HI is tightly bound via A-tracts (filled symbols) which nucleate cooperative assembly onto adjacent nucleosomes (open symbols).…”

“…Histone HI binds to naked DNA and to chromatin in a highly cooperative manner (Lennard and Thomas, 1985). Such a mode of binding could be a key parameter in the general repression of chromatin (Renz, 1975;Alberts et al, 1977;Weintraub, 1985).…”

Histone H1 expressed in Saccharomyces cerevisiae binds to chromatin and affects survival, growth, transcription, and plasmid stability but does not change nucleosomal spacing.

“…The globular region appears to be sufficient for sealing the nucleosome in vitro (1) and was suggested to organize the 30-nm fibers (33,58). The Nterminal tail and, in particular, the positively charged Cterminal tail might bind to linker DNA or adjacent nucleosomes and thereby contribute to the condensation of chromatin fibers (27,58). This description of the roles of Hi is based largely on in vitro experiments.…”