Cleavage of Transcriptional Activator Oct-1 by Poliovirus Encoded Protease 3Cpro

In HeLa cells, RNA polymerase II mediated transcription is severely inhibited by poliovirus infection. Both basal and activated transcription are affected to bring about a complete shutoff of host cell transcription. We demonstrate here that the octamer binding transcription factor, Oct-1, is cleaved in HeLa cells infected with poliovirus. Incubation of Oct-1 with the purified, recombinant 3Cpro results in the generation of the cleaved Oct-1 product seen in virus infected cells. Poliovirus infection leads to the formation of altered Oct-1 DNA complexes that can also be generated by incubation of Oct-1 with purified 3Cpro. We also show that Oct-1 cleaved by 3Cpro loses its ability to inhibit transcriptional activation by the SV40 B enhancer. These results suggest that cleavage of Oct-1 in poliovirus infected cells leads to the loss of its activity.