POLIOVIRUS-ENCODED PROTEASE 2A(PRO) CLEAVES THE TATA-BINDING PROTEIN DOES NOT INHIBIT HOST-CELL RNA-POLYMERASE-II TRANSCRIPTION IN-VITRO

Transient expression of the poliovirus-encoded protease 2A(Pro) in euk aryotic cells results in inhibition of both cellular transcription and translation. The inhibition of transcription observed in cells expres sing 2A(Pro) could be due to a primary effect dr secondary effect caus ed by inhibition of: translation. Because transcriptional activity of the TATA-binding protein (TBP) is drastically reduced in poliovirus-in fected cells, we determined if 2A(Pro) is able to Cleave TBP in vitro. We demonstrate here that 2A(Pro) directly cleaves the single tyrosine -glycine bond at position 34 of TBP, This cleavage is also seen in pol iovirus-infected HeLa cells. Surprisingly, despite TBP cleavage 2A(Pro ) was unable to inhibit RNA polymerase II transcription in vitro. Unde r similar conditions, however, 2A(Pro) inhibited translation of a capp ed cellular mRNA in vitro. Thus, cleavage of TBP ai position 34 does n ot alter its transcriptional activity in vitro. These results suggest that inhibition of host cell RNA polymerase II transcription seen in c ells transiently transfected with 2A(Pro) is due to host cell translat ional shutoff.