Human hepatic glyceraldehyde-3-phosphate dehydrogenase binds to the poly(U) tract of the 3′ non-coding region of hepatitis C virus genomic RNA

The unique poly(U/UC) tract, the middle part of the tripartite 3' non-coding region (3'NCR) of hepatitis C virus (HCV) genomic RNA, may represent a recognition signal for the HCV replicase complex. In this study, several proteins binding specifically to immobilized ribooligonucleotide r(U)(25) mimicking this structure were identified using cytosolic extracts from HCV-negative or -positive liver explants, and a prominent 36 kDa protein was studied further. Competition experiments including homoribopolymers revealed binding affinities in the order: oligo/poly(U)>(A)>(C)>(G). The protein was identified as glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a multifunctional protein known to bind RNA. GAPDH bound efficiently to the full-length HCV RNA and binding to various 3'NCR constructs revealed critical dependence upon the presence of the middle part of the 3'NCR. Polypyrimidine tract-binding protein, described previously to bind the 3'NCR, did not bind efficiently to the middle part of 3'NCR and was captured from liver extracts in considerably smaller quantities.