[SUBUNITS OF MAMMAL DNA DEPENDENT RNA POLYMERASE III MODIFIED IN VIVO]

In subfractions of DNA-dependent RNA polymerase isolated from nuclei of 3T3 mouse fibroblasts, A431 epidermoid carcinoma cells and mature human placenta, we have identified three subunits modified by both phosphorylation and O-N-acetylglucosamine glucosilation. The subfractions of the human enzyme contained modified subunits with molecular weight of 60 and 45 kDa and a subunit of 52 kDa probably belonging to one of the basal factors of RNA Polymerase III transcription. The subfractions of 3T3 mouse cells RNA Polymerase III consisted of modificated subunits with molecular weight 49, 45 and 42 kDa, however, the 45 kDa subunit might be a component of the basal transcription factor of RNA Polymerase III, since it was not identified in mouse enzyme composition.