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Mol. Cell. Biol., Jan 1998, 58-68, Vol 18, No. 1
WM Chu, R Ballard, BW Carpick, BR Williams and CW Schmid
Cell stress, viral infection, and translational inhibition increase the
abundance of human Alu RNA, suggesting that the level of these transcripts
is sensitive to the translational state of the cell. To determine whether
Alu RNA functions in translational homeostasis, we investigated its role in
the regulation of double-stranded RNA- activated kinase PKR. We found that
overexpression of Alu RNA by cotransient transfection increased the
expression of a reporter construct, which is consistent with an inhibitory
effect on PKR. Alu RNA formed stable, discrete complexes with PKR in vitro,
bound PKR in vivo, and antagonized PKR activation both in vitro and in
vivo. Alu RNAs produced by either overexpression or exposure of cells to
heat shock bound PKR, whereas transiently overexpressed Alu RNA antagonized
virus-induced activation of PKR in vivo. Cycloheximide treatment of cells
decreased PKR activity, coincident with an increase in Alu RNA. These
observations suggest that the increased levels of Alu RNAs caused by
cellular exposure to different stresses regulate protein synthesis by
antagonizing PKR activation. This provides a functional role for mammalian
short interspersed elements, prototypical junk DNA.
Copyright © 1998, American Society for Microbiology
Potential Alu function: regulation of the activity of double-stranded RNA-activated kinase PKR
Department of Chemistry, University of California, Davis 95616, USA.
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