Nuclear interactions are necessary for translational enhancement by spleen necrosis virus RU5.
The 5' long terminal repeat of spleen necrosis virus (SNV) facilitates Rev/Rev-responsive element (RRE)-independent expression of intron-containing human immunodeficiency virus type 1 (HIV-1) gag. The SNV RU5 region, which corresponds to the 165-nucleotide 5' RNA terminus, functions in a position- and orientation-dependent manner to enhance polysome association of intron-containing HIV-1 gag RNA and also nonviral luc RNA. Evidence is mounting that association with nuclear factors during intron removal licenses mRNAs for nuclear export, efficient translation, and nonsense-mediated decay. This project addressed the relationship between the nuclear export pathway of SNV RU5-reporter RNA and translational enhancement. Results of RNA transfection experiments suggest that cytoplasmic proteins are insufficient for SNV RU5 translational enhancement of gag or luc RNA. Reporter gene assays, leptomycin B (LMB) sensitivity experiments, and RNase protection assays indicate that RU5 gag RNA accesses a nuclear export pathway that is distinct from the LMB-inhibited leucine-rich nuclear export sequence-dependent CRM1 pathway, which is used by the HIV-1 RRE. As a unique tool with which to investigate the relationship between different RNA trafficking routes and translational enhancement, SNV RU5 and Rev/RRE were combined on a single gag RNA. We observed a less-than-synergistic effect on cytoplasmic mRNA utilization. Instead, Rev/RRE diverts RU5 gag RNA to the CRM1-dependent, LMB-inhibited pathway and abrogates translational enhancement by SNV RU5. Our study is the first to show that a nuclear factor(s) directs SNV RU5-containing RNAs to a distinct export pathway that is not inhibited by LMB and programs the intron-containing transcript for translational enhancement.
Dangel
Andrew W
AW
Center for Retrovirus Research, The Ohio State University, Columbus, Ohio 43210-1093, USA.
Hull
Stacey
S
Roberts
Tiffiney M
TM
Boris-Lawrie
Kathleen
K
D020121:5' Untranslated Regions / Q000235:genetics*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D015967:Gene Expression Regulation, Viral; D015683:Gene Products, gag / Q000378:metabolism; D015694:Gene Products, rev / Q000378:metabolism; D017930:Genes, Reporter; D006801:Humans; D014176:Protein Biosynthesis; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics* / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
D020121:5' Untranslated Regions; D005231:Fatty Acids, Unsaturated; D015683:Gene Products, gag; D015694:Gene Products, rev; D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins; C038753:leptomycin B