LaGrandeur T E, Parker R
Department of Molecular and Cellular Biology and Howard Hughes Medical Institute, University of Arizona, Tucson, AZ 85721, USA.
EMBO J. 1998 Mar 2;17(5):1487-96. doi: 10.1093/emboj/17.5.1487.
A major mechanism of mRNA decay occurs by the process of deadenylation, decapping and 5' --> 3' exonucleolytic degradation. Recently, the product of the DCP1 gene has been shown to be required for decapping mRNAs in vivo and co-purifies with decapping activity in vitro. We have purified Dcp1p to homogeneity and shown that it is sufficient for decapping, thereby indicating that Dcp1p is the decapping enzyme. Characterization of Dcp1p activity in vitro indicated that the 7-methyl group of the cap structure contributes to the enzyme's substrate specificity. In addition, Dcp1p was effectively inhibited by uncapped mRNAs, and the enzyme efficiently cleaved substrates that were >/=25 nucleotides in length, with a preference for longer mRNA substrates. These properties suggest that Dcp1p recognizes the mRNA substrate by interactions with both the cap and the RNA moiety. The Dcp1p is also a phosphoprotein, suggesting its activity may be regulated by post-transcriptional modification.
mRNA降解的一个主要机制是通过去腺苷酸化、脱帽以及5'→3'核酸外切酶降解的过程发生的。最近，DCP1基因的产物已被证明在体内对mRNA脱帽是必需的，并且在体外与脱帽活性共同纯化。我们已将Dcp1p纯化至同质，并表明它足以进行脱帽，从而表明Dcp1p是脱帽酶。体外Dcp1p活性的表征表明，帽结构的7-甲基基团有助于酶的底物特异性。此外，Dcp1p被无帽mRNA有效抑制，并且该酶能有效切割长度≥25个核苷酸的底物，更倾向于较长的mRNA底物。这些特性表明，Dcp1p通过与帽和RNA部分的相互作用来识别mRNA底物。Dcp1p也是一种磷蛋白，表明其活性可能受转录后修饰的调节。
