On the Activity of RNA Polymerase B in Lysates from Ehrlich Ascites Cells

Abstract

Transcription by endogenous RNA polymerase B in lysates of Ehrlich ascites cells was investigated. The enzyme exhibits 2 salt optima at 0.025 M and at 0.3 M (NH4)2SO4, respectively. Preincubation of the cells with the nucleoside analogue 5,6-dichloro-1-.beta.-D-ribofuranosylbenzimidazole results in an inactivation of the polymerase molecules active under condition of low salt. This indicates 2 functional states of the enzyme in vivo. Initiations of RNA chains by polymerase B do not occur in vitro as judged by the incorporation of [.beta.-32P]GTP. Thus the 2 functional states seem to be both elongating polymerase molecules. Polymerase B does not occur in the lysates in a state ready to initiate on an exogenous template, in contrast to polymerase A and C which do occur in free form. Pretreatment with dichlororibofuranosylbenzimidazole in vivo does not result in an accumulation of free polymerase B.