Differential inhibition of transcription of DNA by melanoma chromosomal proteins.

Histones and 4 nuclear nonhistone protein fractions (NHP1-4) were extracted from nuclei of a Cloudman mouse melanoma cell line (NCTC 3960, CCL 53) and tested for their ability to bind to DNA and influence transcription. The histones and NHP fractions showed different binding affinities for DNA, with the histones and NHP1 exhibiting the highest affinity. The NHP fractions differentially affected both the rate of RNA synthesis and the size of RNA transcribed. NHP1 which inhibited RNA synthesis to the greatest extent, inhibited synthesis of all sizes of RNA except for major peaks of 28S and 8S RNS and discrete minor peaks of 7S, 6S, 5S, and 4S RNS. Histones markedly enhanced the effect of NHP1 on RNA synthesis. These results suggest that there are nonhistone proteins in Cloudman melanoma nuclei which have a high affinity for DNA and which may be involved in the regulation of transcription.