Papers In Press, published online ahead of print October 23, 2001
J. Biol. Chem, 10.1074/jbc.M107535200
Submitted on August 7, 2001
Revised on October 19, 2001
Accepted on October 23, 2001
The mRNA of DEAD box protein p72 is alternatively translated into an 82 kDa RNA helicase
Heike Uhlmann-Schiffler, Oliver G. Rössler, and Hans Stahl
Medical Biochemistry and Molecular Biology, University of the Saarland, Homburg D-66421
Corresponding Author: bchsta{at}uniklinik-saarland.de
p68 and p72 are two highly related DEAD box proteins with similar biochemical activities in the nucleus of vertebrate cells; it is unknown whether they have redundant or differential in vivo functions. We report on a third member of this subfamily which is alternatively expressed from p72 mRNA. A detailed analysis of HeLa p72 mRNA was performed. It has an overall length of more than 5 kb and contains a 0.75 kb 5' untranslated region (UTR) and a 3'UTR of 2.5 kb. Its open reading frame extends to nucleotide -243 upstream of the first in-frame AUG (A in the AUG triplet is +1) which serves as the p72 translation initiator codon. We provide evidence that alternative translation at a non-AUG within the extra coding region of this mRNA yields an 82 kDa protein (p82). Immunological studies substantiate that p82 is a naturally existing p72 variant and that both proteins are expressed at similar concentrations. p82 purified from HeLa cells is an ATP-dependent RNA helicase with biochemical properties almost identical to those of p72.
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