Changes in chromatin properties after partial extraction of non-histone proteins.
By treatment with tRNA in the presence of 1 mM MgCl2, a chromatin preparation was obtained containing all five major histone fractions but lacking a considerable portion of non-histone proteins. This chromatin preparation as well as chromatin extracted with 0.6 M NaCl (depleted of H1 histone and some non-histone proteins) were characterized in respect of solubility and chromatin DNA accessibility. Both samples possessed practically the same solubility in the presence of 0.15 M NaCl and 1 mM MgCl2. The solubility of tRNA-treated chromatin in 5 and 10 mM MgCl2 was higher than that of salt-extracted chromation. The accessibility of the DNA of these chromatin preparations was tested with DNA-dependent RNA polymerase of Escherichia coli as a probe, using procedure that permits measurement of binding site frequency. Both tRNA-treated and salt-extracted chromatin contained as many as 33% and untreated chromatin as few as 4% of the number of binding sites found on protein-free DNA. These results demonstrate that at least in part the non-histone proteins are responsible for salt-induced insolubility and low DNA accessibility of chromatin, thus revealing the importance of non-histone proteins in the maintenance of an overall chromatin structure.
D000818:Animals; D002843:Chromatin / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases; D004926:Escherichia coli / Q000201:enzymology; D008099:Liver / Q000378:metabolism*; D008297:Male; D012343:RNA, Transfer; D051381:Rats; D013698:Templates, Genetic; D014158:Transcription, Genetic
D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D012343:RNA, Transfer; D012321:DNA-Directed RNA Polymerases