title: An importin β protein negatively regulates MicroRNA activity in Arabidopsis.
abstract: As key components in the eukaryotic gene regulatory network, microRNAs (miRNAs) themselves are regulated at the level of both metabolism and activity. To identify factors that modulate miRNA activity, we used an Arabidopsis thaliana transgenic line expressing an artificial miRNA that causes trichome clustering and performed a screen for mutants with compromised miRNA activity (cma mutants) or enhanced miRNA activity (ema mutants). From this screen, we identified two novel mutant alleles of SERRATE, which is known to be required for miRNA biogenesis and dozens of other cma and ema mutants. In this study, we analyzed ema1. SAD2/EMA1 encodes an Importin β protein. The ema1 mutation had no effects on the accumulation of miRNAs and ARGONAUTE1 (AGO1) or on their cytoplasmic and nuclear distributions. Intriguingly, we found that the miRNA effector complexes purified from ema1 contained a larger amount of miRNAs and displayed elevated mRNA cleavage activities, indicating that EMA1 modulates miRNA activity by influencing the loading of miRNAs into AGO1 complexes. These results implicate EMA1 as a negative regulator of the miRNA pathway and reveal a novel layer of miRNA activity modulation.
authors: Graduate Program, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China.
authors: Wei
authors: W
authors: Wang
authors: Ruiqiang
authors: R
authors: Ye
authors: Ying
authors: Y
authors: Xin
authors: Xiaofeng
authors: X
authors: Fang
authors: Chunlian
authors: C
authors: Li
authors: Huiqing
authors: H
authors: Shi
authors: Xueping
authors: X
authors: Zhou
authors: Yijun
authors: Y
authors: Qi
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060565:Argonaute Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D002874:Chromosome Mapping; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism*; D035683:MicroRNAs / Q000378:metabolism*; D016296:Mutagenesis; D009154:Mutation; D010641:Phenotype; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D036226:Seedlings / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D017422:Sequence Analysis, DNA
chemical_list: C117457:AGO1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D028884:Karyopherins; D035683:MicroRNAs; D012333:RNA, Messenger; D018749:RNA, Plant; C514676:SAD2 protein, Arabidopsis