RNA polymerase activities and chromatin protein composition of rat liver during methionine deprivation and refeeding

The reversible effect of dietary methionine deficiency was studied in young adult rats. The sensitivity of nuclear chromatin to micrococcal nuclease (EC3.1.4.7) digestion and the composition of the chromatin proteins were unaffected by the dietary regimens. The specific chromatin-bound RNA polymerase II activity decreased during methionine deficiency. Refeeding of methionine for 2 days restored the activity in the nuclease-released chromatin. RNA polymerase I plus III activity remained unchanged. Total RNA polymerase activity changed with the liver wet weight which was reduced during methionine deficiency and was not restored to control level after 2 days of methionine refeeding. RNA polymerase activity was altered by methionine deficiency. The recovery was independent of major modifications of the chromatin structure and protein composition.