Effects of nonhistone proteins on the circular dichroism spectrum and transcriptional activity of a DNA-histone complex.

Nonhistone chromasomal proteins (NHP) of Ehrlich ascites tumor cells were fractionated into four subfractions by successive extractions with 0.35 M, 0.45 M, and 0.60 M NaCl, and finally 2.0 M NaCl + 5.0 M urea. The CD spectra and transcriptional activities of complexes reconstituted from DNA, histone, and each of these four NHP subfractions obtained from Ehrlich tumor cells were measured in order to identify the effect of each NHP subfraction. The positive ellipticity in the CD of the DNA-histone complex was considerably increased when reconstituted with 0.35 M- or 0.45 M-NHP. The 0.35 M- and 0.45 M-NHP also increased the transcriptional activity of DNA-histone complex. The activities of DNA-histone-0.35 M NHP complex increased progressively with increase in the 0.35 M NHP/DNA ratio. These results suggest that there is a correlation between the increase in transcriptional activity of DNA-histone complexes with 0.35 M- or 0.45 M-NHP and the increase in the percentage of DNA in the B conformation in complexes.