Vol. 107, No. 4, 1982 August 31, 1982 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages 1279-1284 HMG-PROTEINS l AND 2 ARE REQUIRED FOR TRANSCRIPTION OF CHROMATIN BY ENDOGENOUS RNA POLYMERASE Jose A. Stoute and William F. Marzluff Department of Chemistry Florida State University Tallahassee, Florida 32306 Received July 7, 1982 SUMMARY: Chromatin prepared from isolated mouse myeloma cell nuclei faith- fully transcribes RNA using endogenous RNA polymerase. Extraction of the chromatin with 0.35M KCI 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 pro- ducts, 5S rRNA and tRNA precursors, was also stimulated the same amount. INTRODUCTION: The eucaryotic chromosome consists of DNA complexed with his- tones and packaged into a basic repeating structure, the nucleosome (i). However, there are clear differences between those regions of the chromatin which are active in the transcription and those which are inactive. The active regions are more sensitive to DNase I (2). This sensitivity is conferred by the presence of additional proteins, HMG 14 and 17, in the nucleosome core (3, 4). In addition active regions of the chromatin probably contain the proteins, HMG 1 and 2 (5, 6), which replace histone HI in the linker region between nucleosomes (7). The active structure, as judged by DNase sensitivity, can be readily reconstituted after extraction of the HMG proteins simply by adding back the purified proteins HMG 14 and 17 (3, 4). We report here that the HMG proteins 1 and 2 stimulate transcription in an isolated chromatin system (8) with endogenous RNA polymerase which has been depleted of these proteins. METHODS Preparatio ~ and Extraction of Chromatin____ t Chromatin was prepared from purified nuclei of mouse myeloma cells as previously described (8). The chromatin was suspended by shearing through 0006-291X/82/161279-06501.00/0 Copyright © 1982byAcadem~ Pre~,Inc. 1279 AHrigh~ofreproduction m anyform reserved.