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J. Virol., Mar 1996, 1624-1632, Vol 70, No. 3
S Das, DJ Kenan, D Bocskai, JD Keene and A Dasgupta
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.
Copyright © 1996, American Society for Microbiology
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
Department of Microbiology and Immunology, UCLA School of Medicine 90024-1747, USA.
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