Sequences within a small yeast RNA required for inhibition of internal initiation of translation: interaction with La and other cellular proteins influences its inhibitory activity.
We recently reported purification, determination of the nucleotide sequence, and cloning of a 60-nucleotide RNA (I-RNA) from the yeast Saccharomyces cerevisiae which preferentially blocked cap-independent, internal ribosome entry site (IRES)-mediated translation programmed by the poliovirus (PV) 5' untranslated region (UTR). The I-RNA appeared to inhibit IRES-mediated translation by virtue of its ability to bind a 52-kDa polypeptide which interacts with the 5' UTR of viral RNA. We demonstrate here that the HeLa 52-kDa I-RNA-binding protein is immunologically identical to human La autoantigen. Moreover, I-RNA-mediated purified La protein. By using I-RNAs with defined deletions, we have identified sequences of I-RNA required for inhibition of internal initiation of translation. Two smaller fragments of I-RNA (16 and 25 nucleotides) inhibited PV UTR-mediated translation from both monocistronic and bicistronic RNAs. When transfected into HeLa cells, these derivatives of I-RNA inhibited translation of PV RNA. A comparison of protein binding by active and inactive I-RNA mutants demonstrates that in addition to the La protein, three other polypeptides with apparent molecular masses of 80, 70, and 37 kDa may influence the translation-inhibitory activity of I-RNA.
Das
S
S
Department of Microbiology and Immunology, UCLA School of Medicine 90024-1747, USA.
Kenan
D J
DJ
Bocskai
D
D
Keene
J D
JD
Dasgupta
A
A
D001324:Autoantigens / Q000276:immunology*; D003432:Cross-Linking Reagents; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D017955:Poliovirus / Q000235:genetics*; D014176:Protein Biosynthesis; D012331:RNA, Fungal / Q000235:genetics / Q000502:physiology*; D012367:RNA, Viral / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000276:immunology / Q000502:physiology; D012261:Ribonucleoproteins / Q000276:immunology*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D013329:Structure-Activity Relationship; D014466:Ultraviolet Rays; D000097585:SS-B Antigen
D001324:Autoantigens; D003432:Cross-Linking Reagents; D012331:RNA, Fungal; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D000097585:SS-B Antigen