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Molecular and Cellular Biology, October 2005, p. 8779-8791, Vol. 25, No. 20
0270-7306/05/$08.00+0 doi:10.1128/MCB.25.20.8779-8791.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Department of Biology, City University of New York Graduate Center, CSI, 2800 Victory Boulevard, Staten Island, New York 10314,1 Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey 08854,2 Departments of Biochemistry and Molecular Genetics and Pediatrics, University of Colorado School of Medicine, 12801 East 17th Avenue, Aurora, Colorado 800453
Received 17 June 2005/ Returned for modification 14 July 2005/ Accepted 28 July 2005
Hydrolysis of the mRNA cap plays a pivotal role in initiating and completing mRNA turnover. In nematodes, mRNA metabolism and cap-interacting proteins must deal with two populations of mRNAs, spliced leader trans-spliced mRNAs with a trimethylguanosine cap and non-trans-spliced mRNAs with a monomethylguanosine cap. We describe here the characterization of nematode Dcp1 and Dcp2 proteins. Dcp1 was inactive in vitro on both free cap and capped RNA and did not significantly enhance Dcp2 activity. Nematode Dcp2 is an RNA-decapping protein that does not bind cap and is not inhibited by cap analogs but is effectively inhibited by competing RNA irrespective of RNA sequence and cap. Nematode Dcp2 activity is influenced by both 5' end sequence and its context. The trans-spliced leader sequence on mRNAs reduces Dcp2 activity
10-fold, suggesting that 5'-to-3' turnover of trans-spliced RNAs may be regulated. Nematode Dcp2 decaps both m7GpppG- and m2,2,7GpppG-capped RNAs. Surprisingly, both budding yeast and human Dcp2 are also active on m2,2,7GpppG-capped RNAs. Overall, the data suggest that Dcp2 activity can be influenced by both sequence and context and that Dcp2 may contribute to gene regulation in multiple RNA pathways, including monomethyl- and trimethylguanosine-capped RNAs.
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