Section 6
Chapter 5,104

Demonstration in vitro that eucaryotic initiation factor 3 is active but that a cap-binding protein complex is inactive in poliovirus-infected HeLa cells

Etchison, D.; Hansen, J.; Ehrenfeld, E.; Edery, I.; Sonenberg, N.; Milburn, S.; Hershey, J.W.

Journal of Virology 51(3): 832-837


ISSN/ISBN: 0022-538X
PMID: 6088805
Accession: 005103036

Protein synthesis initiation factor preparations from poliovirus-infected HeLa cells have reduced ability to initiate translation on capped mRNA. The defect in initiation factors has been variously attributed to inactivation of eukaryotic initiation factor 3 (eIF3), eIF4B, or a cap-binding protein (CBP) complex. A series of in vitro protein synthesis assays was developed to show that eIF3 is active but a CBP complex activity is inactivated after poliovirus infection, eIF3 activity, when determined in the presence of purified CBP complex, is present in sucrose gradients of factors from both infected and uninfected cells. CBP complex activity, determined in the presence of eIF3 from poliovirus-infected cells, is present in uninfected cells only and comigrates on sucrose gradient with an activity which restores the ability of crude initiation factors from infected cells to translate capped globin mRNA. This is the 1st demonstration by a fractionated translation system that an activity which is attributable to CBP complex is inactivated in poliovirus-infected cells. The results also indicate that eIF3 is undetectable or has greatly reduced activity in the absence of CBP complex.

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