Selective translation of eukaryotic mRNAs: functional molecular analysis of GRSF-1, a positive regulator of influenza virus protein synthesis.
To understand the regulation of cap-dependent translation initiation mediated by specific 5' untranslated region (UTR) RNA-protein interactions in mammalian cells, we have studied the selective translation of influenza virus mRNAs. Previous work has shown that the host cell mRNA binding protein guanine-rich sequence factor 1 (GRSF-1) bound specifically to conserved viral 5' UTR sequences and stimulated translation of viral 5' UTR-driven mRNAs in vitro. In the present study, we have characterized the functional domains of GRSF-1 and mapped the RNA binding activity of GRSF-1 to RRM 2 (amino acids 194 to 275) with amino-terminal deletion glutathione S-transferase (GST)-GRSF-1 proteins. When these mutants were assayed for functional activity in vitro, deletion of an Ala-rich region (Delta[2-94]) appeared to diminish translational stimulation, while deletion of the Ala-rich region in addition to RRM 1 (Delta[2-194]) resulted in a 4-fold increase in translational activation over wild-type GRSF-1 (an overall 20-fold increase in activity). We have also mapped the GRSF-1 RNA binding site on influenza virus NP and NS1 5' UTRs, which was determined to be the sequence AGGGU. With polysome fractionation and cDNA microarray analysis, we have identified cellular and viral mRNAs containing putative GRSF-1 binding sites that were transcriptionally up-regulated and selectively recruited to polyribosomes following influenza virus infection. Taken together, these studies demonstrate that RRM 2 is critical for GRSF-1 RNA binding and translational activity. Further, our data suggest GRSF-1 functions by selectively recruiting cellular and viral mRNAs containing 5' UTR GRSF-1 binding sites to polyribosomes, which is mediated through interactions with cellular proteins.
Kash
John C
JC
Department of Microbiology, University of Washington School of Medicine, Seattle, Washington 98195, USA.
Cunningham
Dawn M
DM
Smit
Maria W
MW
Park
Youngwoo
Y
Fritz
David
D
Wilusz
Jeffrey
J
Katze
Michael G
MG
D020121:5' Untranslated Regions / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D005057:Eukaryotic Cells; D006367:HeLa Cells; D006801:Humans; D009980:Influenza A virus / Q000235:genetics; D008969:Molecular Sequence Data; D019590:Nucleocapsid Proteins; D009698:Nucleoproteins / Q000235:genetics; D009975:Orthomyxoviridae / Q000235:genetics*; D039102:Poly(A)-Binding Proteins; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D012367:RNA, Viral / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014758:Viral Core Proteins / Q000235:genetics; D014763:Viral Matrix Proteins / Q000235:genetics; D017361:Viral Nonstructural Proteins / Q000235:genetics; D014764:Viral Proteins / Q000096:biosynthesis / Q000235:genetics
D020121:5' Untranslated Regions; C088356:GRSF1 protein, human; C085820:INS1 protein, influenza virus; C031540:M-protein, influenza virus; C048842:NP protein, Influenza A virus; D019590:Nucleocapsid Proteins; D009698:Nucleoproteins; D039102:Poly(A)-Binding Proteins; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D014758:Viral Core Proteins; D014763:Viral Matrix Proteins; D017361:Viral Nonstructural Proteins; D014764:Viral Proteins