NAD+-dependent RNA terminal 2′ and 3′ phosphomonoesterase activity of a subset of Tpt1 enzymes
NAD+-dependent RNA terminal 2′ and 3′ phosphomonoesterase activity of a subset of Tpt1 enzymes
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DOI：
10.1261/rna.071142.119
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发表时间：
2019-07-01
期刊：
影响因子：
4.5
通讯作者：
Shuman, Stewart
中科院分区：
文献类型：
--
作者：
Munir, Annum;Abdullahu, Leonora;Shuman, Stewart
The enzyme Tpt1 removes the 2'-PO4 at the splice junction generated by fungal tRNA ligase; it does so via a two-step reaction in which (i) the internal RNA 2'-PO4 attacks NAD(+) to form an RNA-2'-phospho-ADP-ribosyl intermediate; and (ii) transesterification of the ribose O2 '' to the 2'-phosphodiester yields 2'-OH RNA and ADP-ribose-1 '',2 ''-cyclic phosphate products. The role that Tpt1 enzymes play in taxa that have no fungal-type RNA ligase remains obscure. An attractive prospect is that Tpt1 enzymes might catalyze reactions other than internal RNA 2'-PO4 removal, via their unique NAD(+)-dependent transferase mechanism. This study extends the repertoire of the Tpt1 enzyme family to include the NAD(+)-dependent conversion of RNA terminal 2' and 3' monophosphate ends to 2'-OH and 3'-OH ends, respectively. The salient finding is that different Tpt1 enzymes vary in their capacity and positional specificity for terminal phosphate removal. Clostridium thermocellum and Aeropyrum pernix Tpt1 proteins are active on 2'-PO4 and 3'-PO4 ends, with a 2.4- to 2.6-fold kinetic preference for the 2'-PO4. The accumulation of a terminal 3'-phospho-ADP-ribosylated RNA intermediate during the 3'-phosphotransferase reaction suggests that the geometry of the 3'-p-ADPR adduct is not optimal for the ensuing transesterification step. Chaetomium thermophilum Tpt1 acts specifically on a terminal 2'-PO4 end and not with a 3'-PO4. In contrast, Runella slithyformis Tpt1 and human Tpt1 are ineffective in removing either a 2'-PO4 or 3'-PO4 end.
