Margossian S P, Li H, Zassenhaus H P, Butow R A
Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas 75235, USA.
Cell. 1996 Jan 26;84(2):199-209. doi: 10.1016/s0092-8674(00)80975-7.
The yeast mitochondrial protein Suv3p is a putative NTP-dependent RNA helicase. Here we report that in cells lacking Suv3p, there is an approximately 50-fold increase in the excised form of the group I intron omega of the mitochondrial 31S rRNA gene. Surprisingly, little mature 21S rRNA accumulates in those cells; instead, unligated 21S rRNA exons appear. Intron overaccumulation could lead to spliced exon reopening via a reaction known to be catalyzed by group I introns in vitro. We also show that Suv3p is a functional component of a novel mitochondrial NTP-dependent 3'-to-5' exoribonuclease activity that can degrade group I intron RNAs. These findings account for group I intron overaccumulation in cells lacking Suv3p and define a novel function for putative RNA helicases in direct RNA degradation.
酵母线粒体蛋白Suv3p是一种推测的依赖NTP的RNA解旋酶。我们在此报告，在缺乏Suv3p的细胞中，线粒体31S rRNA基因的I类内含子ω的切除形式增加了约50倍。令人惊讶的是，那些细胞中几乎没有成熟的21S rRNA积累；相反，出现了未连接的21S rRNA外显子。内含子过度积累可能通过一种已知在体外由I类内含子催化的反应导致剪接后的外显子重新打开。我们还表明，Suv3p是一种新型线粒体依赖NTP的3'至5'外切核糖核酸酶活性的功能成分，该活性可降解I类内含子RNA。这些发现解释了缺乏Suv3p的细胞中I类内含子的过度积累，并定义了推测的RNA解旋酶在直接RNA降解中的新功能。
