New Insights Into Protein Synthesis and Hepatitis C Infections

From left, Jennifer Doudna, Bunpote

 Siridechadilok and Eva Nogales, used this cryo 

electron microscope to create a 3-D model of

 the protein complex eIF3 that shed new light 

on protein synthesis and Hepatitis C viral

 infections. Photo courtesy of lbl.gov

This article shows how cryo electron microscopy (cryo-EM) was used to create a 3-D model of the protein complex called eukaryotic translation initiation factor 3 (eIF3).  The cryo-EM reconstructions of Biochemist Jennifer Doudna and biophysicist Eva Nogales show that eIF3 consists of five lobes; a head and a pair of arms and legs. 

The study shows that the left “arm" of the eIF3 complex binds to the eukaryotic protein complex that recognizes the methylated guanosine cap at the 5’end of the eukaryotic mRNAs.  By drawing the mRNA’s 5’end cap through the ribosome entry site and towards the exit, eIF3 ensures the mRNA is properly positioned for its genetic code to be translated. EIF3 will also wrap its arms and legs around a structural element of RNA for the hepatitis C virus (HVC), known as the internal ribosome entry site, and pin it to the exit site of the 40S ribosome subunit. The IRES leaves through the left arm of the eIF3 complex at the same location where interaction with the human mRNA cap-binding complex takes place. 

This act might explain the ability of the HVC IRES to hijack the human ribosome and its associated translation factor. This new information gives insight into how the initiation mechanisms of protein synthesis work specifically for humans. It also provides a step towards understanding what happens when a viral infection occurs at the molecular level. By understanding these methods, scientists may be able to come up with new and improved therapies for viral infections.

Blog post Author: Jenn Gregorio Section 124-26

Work Cited:
"New Insights Into Protein Synthesis and Hepatitis C Infections." Research News:. N.p., 5 Dec. 2005. Web. 03 Mar. 2013.