Department of Cell and Molecular Biology, Uppsala University, Box 596, SE-751 24 Uppsala, Sweden.
J Biol Chem. 2010 Jan 1;285(1):163-70. doi: 10.1074/jbc.M109.043893. Epub 2009 Nov 9.
Poly(A)-specific ribonuclease (PARN) is a mammalian 3'-exoribonuclease that degrades poly(A) with high specificity. To reveal mechanisms by which poly(A) is recognized by the active site of PARN, we have performed a kinetic analysis using a large repertoire of trinucleotide substrates. Our analysis demonstrated that PARN harbors specificity for adenosine recognition in its active site and that the nucleotides surrounding the scissile bond are critical for adenosine recognition. We propose that two binding pockets, which interact with the nucleotides surrounding the scissile bond, play a pivotal role in providing specificity for the recognition of adenosine residues by the active site of PARN. In addition, we show that PARN, besides poly(A), also quite efficiently degrades poly(U), approximately 10-fold less efficiently than poly(A). The poly(U)-degrading property of PARN could be of biological significance as oligo(U) tails recently have been proposed to play a role in RNA stabilization and destabilization.
聚腺苷酸特异性核糖核酸酶（PARN）是一种具有高度特异性的哺乳动物 3'-外切核糖核酸酶，可降解聚腺苷酸。为了揭示聚腺苷酸被 PARN 活性位点识别的机制，我们使用大量三核苷酸底物进行了动力学分析。我们的分析表明，PARN 在其活性位点中具有腺苷识别特异性，并且位于切口键周围的核苷酸对于腺苷识别至关重要。我们提出，与切口键周围的核苷酸相互作用的两个结合口袋在为 PARN 的活性位点识别腺苷残基提供特异性方面发挥着关键作用。此外，我们还表明，PARN 除了聚腺苷酸外，还能相当有效地降解聚尿苷酸，效率约比聚腺苷酸低 10 倍。PARN 的聚尿苷酸降解特性可能具有生物学意义，因为最近提出寡尿苷酸尾巴在 RNA 稳定和不稳定中起作用。
