Several lines of evidence are presented which support the contention that chromatin may be dissociated, fractionated, and reconstituted without altering the compositional, structural, or transcriptional integrity of the genome. The similar compositions of native and reconstituted chromatins are suggested by the absence of significant differences in their protein/DNA ratios and in the polyacrylamide gel electrophoretic profiles of their histones and nonhistone chromosomal proteins. Criteria for fidelity of genome structure in reconstituted chromatin include binding of reporter molecules with specificity for the minor groove of DNA, binding of histones, number of sites available for addition of nucleotides, and circular dichroism spectra. When the transcriptional activities of native and reconstituted chromatins were compared under conditions where reinitiation is prohibited, significant changes were not observed. Taken together, the present results strongly suggest, but do not conclusively establish, fidelity of chromatin reconstitution.
Effects of the SH inhibitor sodium iodoacetate, alone and with adjuncts menadiol diphosphate, sodium malonate, sodium fluoride and heparin, on incorporation of tryptophane-3 H into nonhistone chromosomal proteins of HeLa cells were examined. The drugs block incorporation of tryptophane-3 H into nonhistone chromosomal proteins far more than incorporation of leucine-3 H into total cellular proteins. Drug effects on thymidine phosphorylation and DNA synthesis in HeLa cells exceed corresponding effects on fibroblasts from normal healing wounds.
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