Synergistic and Independent Actions of Multiple Terminal Nucleotidyl Transferases in the 3’ Tailing of Small RNAs in Arabidopsis

Authors

Xiaoyan Wang, Institute of Plant Biology and Department of Biochemistry, School of Life Sciences, Fudan University
Shuxin Zhang, Center for Plant Science Innovation & School of Biological Sciences, University of Nebraska-Lincoln
Yongchao Dou, Center for Plant Science Innovation & School of Biological Sciences, University of Nebraska-Lincoln
Chi Zhang, Center for Plant Science Innovation & School of Biological Sciences, University of Nebraska-LincolnFollow
Xuemei Chen, Department of Botany and Plant Sciences & Institute of Integrative Genome Biology, University of California; Howard Hughes Medical Institute, University of California
Bin Yu, Center for Plant Science Innovation & School of Biological Sciences, University of Nebraska-LincolnFollow
Guodong Ren, Institute of Plant Biology and Department of Biochemistry, School of Life Sciences, Fudan University; Collaborative Innovation Center for Genetics and Development, School of Life SciencesFollow

Document Type

Article

Date of this Version

2015

Citation

PLOS Genetics, 2015

Comments

U.S. Government work

Abstract

All types of small RNAs in plants, piwi-interacting RNAs (piRNAs) in animals and a subset of siRNAs in Drosophila and C. elegans are subject to HEN1 mediated 3’ terminal 2’-Omethylation. This modification plays a pivotal role in protecting small RNAs from 3’ uridylation, trimming and degradation. In Arabidopsis, HESO1 is a major enzyme that uridylates small RNAs to trigger their degradation. However, U-tail is still present in null hen1 heso1 mutants, suggesting the existence of (an) enzymatic activities redundant with HESO1. Here, we report that UTP: RNA uridylyltransferase (URT1) is a functional paralog of HESO1. URT1 interacts with AGO1 and plays a predominant role in miRNA uridylation when HESO1 is absent. Uridylation of miRNA is globally abolished in a hen1 heso1 urt1 triple mutant, accompanied by an extensive increase of 3’-to-5’ trimming. In contrast, disruption of URT1 appears not to affect the heterochromatic siRNA uridylation. This indicates the involvement of additional nucleotidyl transferases in the siRNA pathway. Analysis of miRNA tailings in the hen1 heso1 urt1 triple mutant also reveals the existence of previously unknown enzymatic activities that can add non-uridine nucleotides. Importantly, we show HESO1 may also act redundantly with URT1 in miRNA uridylation when HEN1 is fully competent. Taken together, our data not only reveal a synergistic action of HESO1 and URT1 in the 3’ uridylation of miRNAs, but also independent activities of multiple terminal nucleotidyl transferases in the 3’ tailing of small RNAs and an antagonistic relationship between uridylation and trimming. Our results may provide further insight into the mechanisms of small RNA 3’ end modification and stability control.