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RNA 3'-phosphate cyclase (RtcA) catalyzes ligase-like adenylylation of DNA and RNA 5'-monophosphate ends.

ABSTRACT: RNA 3'-phosphate cyclase (Rtc) enzymes are a widely distributed family that catalyze the synthesis of RNA 2',3'-cyclic phosphate ends via an ATP-dependent pathway comprising three nucleotidyl transfer steps: reaction of Rtc with ATP to form a covalent Rtc-(histidinyl-N)-AMP intermediate and release PP(i); transfer of AMP from Rtc to an RNA 3'-phosphate to form an RNA(3')pp(5')A intermediate; and attack by the terminal nucleoside O2' on the 3'-phosphate to form an RNA 2',3'-cyclic phosphate product and release AMP. The chemical transformations of the cyclase pathway resemble those of RNA and DNA ligases, with the key distinction being that ligases covalently adenylylate 5'-phosphate ends en route to phosphodiester synthesis. Here we show that the catalytic repertoire of RNA cyclase overlaps that of ligases. We report that Escherichia coli RtcA catalyzes adenylylation of 5'-phosphate ends of DNA or RNA strands to form AppDNA and AppRNA products. The polynucleotide 5' modification reaction requires the His(309) nucleophile, signifying that it proceeds through a covalent RtcA-AMP intermediate. We established this point directly by demonstrating transfer of [(32)P]AMP from RtcA to a pDNA strand. RtcA readily adenylylated the 5'-phosphate at a 5'-PO(4)/3'-OH nick in duplex DNA but was unable to covert the nicked DNA-adenylate to a sealed phosphodiester. Our findings raise the prospect that cyclization of RNA 3'-ends might not be the only biochemical pathway in which Rtc enzymes participate; we discuss scenarios in which the 5'-adenylyltransferase of RtcA might play a role.

SUBMITTER: Chakravarty AK

PROVIDER: S-EPMC3039336 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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RNA 3'-phosphate cyclase (RtcA) catalyzes ligase-like adenylylation of DNA and RNA 5'-monophosphate ends.

Chakravarty Anupam K AK Shuman Stewart S

The Journal of biological chemistry 20101122 6

RNA 3'-phosphate cyclase (Rtc) enzymes are a widely distributed family that catalyze the synthesis of RNA 2',3'-cyclic phosphate ends via an ATP-dependent pathway comprising three nucleotidyl transfer steps: reaction of Rtc with ATP to form a covalent Rtc-(histidinyl-N)-AMP intermediate and release PP(i); transfer of AMP from Rtc to an RNA 3'-phosphate to form an RNA(3')pp(5')A intermediate; and attack by the terminal nucleoside O2' on the 3'-phosphate to form an RNA 2',3'-cyclic phosphate produ ...[more]

PMID: 21098490

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Project description:Escherichia coli RtcB exemplifies a family of GTP-dependent RNA repair/splicing enzymes that join 3'-PO4 ends to 5'-OH ends via stable RtcB-(histidinyl-N)-GMP and transient RNA3'pp5'G intermediates. E. coli RtcB also transfers GMP to a DNA 3'-PO4 end to form a stable "capped" product, DNA3'pp5'G. RtcB homologs are found in a multitude of bacterial proteomes, and many bacteria have genes encoding two or more RtcB paralogs; an extreme example is Myxococcus xanthus, which has six RtcBs. In this study, we purified, characterized, and compared the biochemical activities of three M. xanthus RtcB paralogs. We found that M. xanthus RtcB1 resembles E. coli RtcB in its ability to perform intra- and intermolecular sealing of a HORNAp substrate and capping of a DNA 3'-PO4 end. M. xanthus RtcB2 can splice HORNAp but has 5-fold-lower RNA ligase specific activity than RtcB1. In contrast, M. xanthus RtcB3 is distinctively feeble at ligating the HORNAp substrate, although it readily caps a DNA 3'-PO4 end. The novelty of M. xanthus RtcB3 is its capacity to cap DNA and RNA 5'-PO4 ends to form GppDNA and GppRNA products, respectively. As such, RtcB3 joins a growing list of enzymes (including RNA 3'-phosphate cyclase RtcA and thermophilic ATP-dependent RNA ligases) that can cap either end of a polynucleotide substrate. GppDNA formed by RtcB3 can be decapped to pDNA by the DNA repair enzyme aprataxin.RtcB enzymes comprise a widely distributed family of RNA 3'-PO4 ligases distinguished by their formation of 3'-GMP-capped RNAppG and/or DNAppG polynucleotides. The mechanism and biochemical repertoire of E. coli RtcB are well studied, but it is unclear whether its properties apply to the many bacteria that have genes encoding multiple RtcB paralogs. A comparison of the biochemical activities of three M. xanthus paralogs, RtcB1, RtcB2, and RtcB3, shows that not all RtcBs are created equal. The standout findings concern RtcB3, which is (i) inactive as an RNA 3'-PO4 ligase but adept at capping a DNA 3'-PO4 end and (ii) able to cap DNA and RNA 5'-PO4 ends to form GppDNA and GppRNA, respectively. The GppDNA and GppRNA capping reactions are novel nucleic acid modifications.

Dataset Information

RNA 3'-phosphate cyclase (RtcA) catalyzes ligase-like adenylylation of DNA and RNA 5'-monophosphate ends.

Publications

RNA 3'-phosphate cyclase (RtcA) catalyzes ligase-like adenylylation of DNA and RNA 5'-monophosphate ends.

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