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Cleavage of transcriptional activator Oct-1 by poliovirus encoded protease 3Cpro
P Yalamanchili1, K Weidman, A Dasgupta
1Department of Microbiology and Immunology, UCLA School of Medicine 90095-1747, USA.
Abstract:
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.
Insights
Poliovirus infection cleaves the Oct-1 transcription factor in HeLa cells, inhibiting host cell transcription. This cleavage, mediated by poliovirus 3Cpro, results in Oct-1 losing its transcriptional regulatory activity.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Poliovirus infection severely inhibits RNA polymerase II transcription in HeLa cells.
- Both basal and activated host cell transcription are affected, leading to a complete shutoff.
Purpose of the Study:
- To investigate the mechanism by which poliovirus inhibits host cell transcription.
- To determine the role of the octamer binding transcription factor Oct-1 in this process.
Main Methods:
- Analyzing Oct-1 cleavage in poliovirus-infected HeLa cells.
- Incubating Oct-1 with purified recombinant poliovirus 3C protease (3Cpro).
- Assessing the DNA-binding activity of Oct-1 and its effect on transcriptional activation.
Main Results:
- Oct-1 is cleaved in poliovirus-infected HeLa cells.
- Purified 3Cpro generates the same cleaved Oct-1 product observed in infected cells.
- Cleaved Oct-1 loses its ability to inhibit transcriptional activation by the SV40 B enhancer.
- Poliovirus infection leads to altered Oct-1 DNA complexes, reproducible with 3Cpro treatment.
Conclusions:
- Poliovirus infection induces cleavage of Oct-1 via the viral 3Cpro.
- Cleavage of Oct-1 results in the loss of its transcriptional regulatory function.
- This mechanism contributes to the shutoff of host cell transcription during poliovirus infection.