HMG-proteins 1 and 2 are required for transcription of chromatin by endogenous RNA polymerase

Chromatin prepared from isolated mouse myeloma cell nuclei faithfully transcribes RNA using endogenous RNA polymerase. Extraction of the chromatin with 0.35M KC1 greatly reduces the ability of the chromatin to transcribe RNA, but RNA synthesis is restored by adding back the extracted material. The major proteins extracted under these conditions are the high mobility group proteins - HMG 1 and 2. When purified HMG proteins 1 and 2 were added back to the extracted chromatin preparations total RNA synthesis was stimulated 3 to 5 fold. The synthesis of the RNA polymerase III products, 5S rRNA and tRNA precursors, was also stimulated the same amount.