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Poliovirus-induced inhibition of polypeptide initiation in vitro on native polyribosomes
Abstract:
The inhibition of HeLa cell protein synthesis by poliovirus was studied by examining initiation in vitro on endogenous host polyribosomes. At an early stage, before major viral RNA replication and protein synthesis begins, the initiation of translation on cellular mRNA is strongly inhibited. Fractionation of extracts from infected cells shows that the lesion is associated mainly with the crude polyribosome fraction. The cellular mRNA appears unchanged and is as active as mRNA from control cells in stimulating incorporation. The native ribosomal subunits and KCl-washed polyribosomes from the infected cells are also active. Only the ribosomal wash fraction prepared from the inhibited polyribosomes had reduced activity. However, the reduction in the ribosomal wash activity measured in a reconstructed system is not as large as the inhibition seen with "native" polyribosomes. The results indicate that a viral induced inhibition is probably associated with the ribosomal wash fraction, but the reconstructed system is not equivalent to the "native" inhibited system.
Insights
Poliovirus strongly inhibits HeLa cell protein synthesis initiation early in infection. This viral-induced inhibition is linked to the ribosomal wash fraction, though not fully replicated in vitro.
Area of Science:
- Molecular Biology
- Virology
- Cell Biology
Background:
- Poliovirus infection leads to a shutdown of host cell protein synthesis.
- Understanding the precise mechanism of this inhibition is crucial for virology research.
Purpose of the Study:
- To investigate the stage and mechanism by which poliovirus inhibits HeLa cell protein synthesis initiation.
- To identify the specific cellular component responsible for the observed inhibition.
Main Methods:
- Studied protein synthesis initiation in vitro using endogenous host polyribosomes from poliovirus-infected HeLa cells.
- Fractionated infected cell extracts to isolate and test different components (mRNA, ribosomal subunits, ribosomal wash).
- Reconstructed systems were used to assess the activity of isolated fractions.
Main Results:
- Host cell translation initiation is strongly inhibited early in poliovirus infection, before viral replication.
- The inhibition is primarily associated with the crude polyribosome fraction from infected cells.
- While the ribosomal wash fraction showed reduced activity, reconstructed systems did not fully replicate the inhibition seen in native polyribosomes.
Conclusions:
- Poliovirus-induced inhibition of host protein synthesis initiation is likely associated with the ribosomal wash fraction.
- The in vitro reconstructed system may not fully recapitulate the complex cellular environment responsible for the inhibition.