The polyadenylation of messenger RNAs is mediated by a multi-subunit complex that is conserved in eukaryotes. Among the most interesting of these proteins is the 30-kDa-subunit of the Cleavage and Polyadenylation Specificity Factor, or CPSF30. In this study, the Arabidopsis CPSF30 ortholog, AtCPSF30, is characterized. This protein possesses an unexpected endonucleolytic activity that is apparent as an ability to nick and degrade linear as well as circular single-stranded RNA. Endonucleolytic action by AtCPSF30 leaves RNA 3′ ends with hydroxyl groups, as they can be labeled by RNA ligase with [32P]-cytidine-3′,5′-bisphosphate. Mutations in the first of the three CCCH zinc finger motifs of the protein abolish RNA binding by AtCPSF30 but have no discernible effects on nuclease activity. In contrast, mutations in the third zinc finger motif eliminate the nuclease activity of the protein, and have a modest effect on RNA binding. The N-terminal domain of another Arabidopsis polyadenylation factor subunit, AtFip1(V), dramatically inhibits the nuclease activity of AtCPSF30 but has a slight negative effect on the RNA-binding activity of the protein. These results indicate that AtCPSF30 is a probable processing endonuclease, and that its action is coordinated through its interaction with Fip1.
|Number of pages||11|
|Journal||Nucleic Acids Research|
|State||Published - Jul 2007|
Bibliographical noteFunding Information:
The authors are grateful to Carol Von Lanken for technical assistance and to Kim Delaney and Dr Kevin Forbes for some materials used in this study. They are especially appreciative of the advice of Dr Dan Schoenberg. This work was supported by NSF grant MCB-0313472. Funding to pay the Open Access publication charges for this article was provided by the National Science Foundation (MCB-0313472).
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