Uhlmann-Schiffler Heike, Rössler Oliver G, Stahl Hans
Fachbereich Medizinische Biochemie und Molekularbiologie, Fachrichtung Theoretische Medizin, Universität des Saarlandes, D-66421 Homburg, Germany.
J Biol Chem. 2002 Jan 11;277(2):1066-75. doi: 10.1074/jbc.M107535200. Epub 2001 Oct 23.
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 that 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 and a 3'-untranslated region 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.
p68和p72是两种高度相关的DEAD盒蛋白，在脊椎动物细胞核中具有相似的生化活性；它们在体内是否具有冗余或不同的功能尚不清楚。我们报道了该亚家族的第三个成员，它是由p72 mRNA选择性表达的。对HeLa p72 mRNA进行了详细分析。它全长超过5 kb，包含一个0.75 kb的5'非翻译区和一个2.5 kb的3'非翻译区。其开放阅读框延伸至第一个符合读码框的AUG（AUG三联体中的A为+1）上游第243位核苷酸，该AUG作为p72的翻译起始密码子。我们提供的证据表明，该mRNA额外编码区内一个非AUG处的选择性翻译产生了一种82 kDa的蛋白（p82）。免疫学研究证实p82是一种天然存在的p72变体，且两种蛋白以相似的浓度表达。从HeLa细胞中纯化的p82是一种依赖ATP的RNA解旋酶，其生化特性与p72几乎相同。
