Distinct and Cooperative Activities of HESO1 and URT1 Nucleotidyl Transferases in MicroRNA Turnover in Arabidopsis
Date
2015-04-30
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PLOS (Public Library of Science)
Abstract
3’ uridylation is increasingly recognized as a conserved RNA modification process associated
with RNA turnover in eukaryotes. 2’-O-methylation on the 3’ terminal ribose protects
micro(mi)RNAs from 3’ truncation and 3’ uridylation in Arabidopsis. Previously, we identified
HESO1 as the nucleotidyl transferase that uridylates most unmethylated miRNAs in vivo,
but substantial 3’ tailing of miRNAs still remains in heso1 loss-of-function mutants. In this
study, we found that among nine other potential nucleotidyl transferases, UTP:RNA URIDYLYLTRANSFERASE
1 (URT1) is the single most predominant nucleotidyl transferase that
tails miRNAs. URT1 and HESO1 prefer substrates with different 3’ end nucleotides in vitro
and act cooperatively to tail different forms of the same miRNAs in vivo. Moreover, both
HESO1 and URT1 exhibit nucleotidyl transferase activity on AGO1-bound miRNAs. Although
these enzymes are able to add long tails to AGO1-bound miRNAs, the tailed miRNAs
remain associated with AGO1. Moreover, tailing of AGO1-bound miRNA165/6
drastically reduces the slicing activity of AGO1-miR165/6, suggesting that tailing reduces
miRNA activity. However, monouridylation of miR171a by URT1 endows the miRNA the
ability to trigger the biogenesis of secondary siRNAs. Therefore, 3’ tailing could affect the
activities of miRNAs in addition to leading to miRNA degradation.
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Tu B, Liu L, Xu C, Zhai J, Li S, Lopez MA, et al. (2015) Distinct and Cooperative Activities of HESO1 and URT1 Nucleotidyl Transferases in MicroRNA Turnover in Arabidopsis. PLoS Genet 11 (4): e1005119. doi:10.1371/journal.pgen.1005119