REPRESSION OF RNA POLYMERASE-III TRANSCRIPTION BY ADENOVIRUS E1A

Adenovirus EIA encodes two major proteins of 289 and 243 amino acids ( 289R and 243R), which both have transcription regulatory properties. E 1A-289R is a transactivator whereas EIA-243R primarily functions as a repressor of transcription. Here we show that EIA repression is not re stricted to RNA polymerase II genes but also includes the adenovirus v irus-associated (VA) RNA genes. These genes are transcribed by RNA pol ymerase III and have previously been suggested to be the target of an EIA-289R-mediated transactivation. Surprisingly, we found that during transient transfection both EIA proteins repressed VA RNA transcriptio n. E1A repression of VA RNA transcription required both conserved regi ons 1 and 2 and therefore differed from the EIA-mediated inhibition of simian virus 40 enhancer activity which primarily required conserved region 1. The repression was counteracted by the E1B-19K protein, whic h also, in the absence of E1A, enhanced the accumulation of VA RNA. Im portantly, we show that efficient VA RNA transcription requires expres sion of both E1A and the E1B-19K protein during virus infection.