Repression of beta interferon gene expression in virus-infected cells is correlated with a poly(A) tail elongation.
AUTOR(ES)
Dehlin, E
RESUMO
Expression of beta interferon (IFN-beta) is transiently induced when Namalwa B cells (Burkitt lymphoma cell line) are infected by Sendai virus. In this study, we found that an elongation of the IFN-beta mRNA could be detected in virus-infected cells and that such a modification was not observed when the IFN-beta transcript was induced by a nonviral agent, poly(I-C). Treatment of the cells with a transcriptional inhibitor (actinomycin D or 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole) resulted in further elongation of the transcript. Characterization of the elongated IFN-beta transcript by primer extension and RNase H treatment showed that the modification was a result of an elongated poly(A) tail of up to 400 nucleotides. We conclude that the poly(A) tail elongation of the IFN-beta transcript is associated with the viral infection. Furthermore, the presence of the elongated IFN-beta transcript correlated with a decrease of IFN-beta protein in the medium and in cell extracts. Sucrose gradient analysis of cytoplasmic extracts showed that IFN-beta transcripts with elongated poly(A) tails were found in the nonpolysomal fractions, whereas the shorter transcripts could be detected in both polysomal and nonpolysomal fractions. A longer form of the IFN-beta mRNA was also found in the nonpolysomal fractions of cells not treated with transcriptional inhibitors. Thus, the observed regulation of IFN-beta mRNA is not entirely dependent on the inhibition of transcription. To our knowledge, this study provides the first example of a poly(A) tail elongation in somatic cells that negatively influences gene expression in vivo.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=231023Documentos Relacionados
- Poly(A) Polymerase from Vaccinia Virus-Infected Cells I. Partial Purification and Characterization
- Poly(A) Polymerase from Vaccinia Virus-Infected Cells II. Product and Primer Characterization
- Translational elongation rate changes in encephalomyocarditis virus-infected and interferon-treated cells.
- mRNA with a <20-nt poly(A) tail imparted by the poly(A)-limiting element is translated as efficiently in vivo as long poly(A) mRNA
- Host factor Hfq of Escherichia coli stimulates elongation of poly(A) tails by poly(A) polymerase I