REGULATION OF TRANSCRIPTION BY DNA-BOUND NON-HISTONE NUCLEAR PROTEINS

Purified nonhistone proteins from mouse mammary cells bind specifically to homologous DNA or chromatin. Complexes of nonhistone protein with DNA or chromatin, isolated on agarose columns, were transcribed with both Escherichia coli RNA polymerase and RNA polymerase B from calf thymus. The fact that complexing of DNA with nonhistone proteins increases transcription by E. coli RNA polymerase but not by RNA polymerase B suggests different mechanisms of transcription by these 2 enzymes. Similar experiments with mouse and Drosophila chromatin indicate that non histone proteins specifically stimulate the transcription of mouse chromatin by RNA polymerase B. Nonhistone proteins stimulate the transcription of mouse mammary tumor virus sequences in chromatin by RNA polymerase B but not by E. coli RNA polymerase. Those nonhistone proteins bound specifically to chromatin are apparently able to activate the transcription of specific genes by eukaryotic RNA polymerase.