Related Experiment Video
Updated: Sep 27, 2025
mirMachine: A One-Stop Shop for Plant miRNA Annotation
Published on: May 1, 2021
Dynamic Phosphorylation of miRNA Biogenesis Factor HYL1 by MPK3 Involving Nuclear-Cytoplasmic Shuttling and Protein
Prakash Kumar Bhagat1,2, Deepanjali Verma1,3, Kirti Singh1
1National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi 110065, India.
Abstract:
MicroRNAs (miRNAs) are one of the prime regulators of gene expression. The recruitment of hyponastic leaves 1 (HYL1), a double-stranded RNA binding protein also termed as DRB1, to the microprocessor complex is crucial for accurate primary-miRNA (pri-miRNA) processing and the accumulation of mature miRNA in Arabidopsis thaliana. In the present study, we investigated the role of the MAP kinase-mediated phosphorylation of AtHYL1 and its sub-cellular activity. AtMPK3 specifically phosphorylates AtHYL1 at the evolutionarily conserved serine-42 present at the N-terminal regions and plays an important role in its nuclear-cytosolic shuttling. Additionally, we identified that AtHYL1 is cleaved by trypsin-like proteases into an N-terminal fragment, which renders its subcellular activities. We, for the first time, report that the dimerization of AtHYL1 not only takes place in the nucleus, but also in the cytosol, and the C-terminal of AtHYL1 has a role in regulating its stability, as well as its subcellular localization. AtHYL1 is hyper-phosphorylated in mpk3 mutants, leading to higher stability and reduced degradation. Our data show that AtMPK3 is a negative regulator of AtHYL1 protein stability and that the AtMPK3-induced phosphorylation of AtHYL1 leads to its protein degradation.
Insights
The MAP kinase MPK3 regulates microRNA (miRNA) production in Arabidopsis by phosphorylating HYL1, controlling its stability and localization. This phosphorylation leads to HYL1 degradation, impacting miRNA processing.
Area of Science:
- Plant molecular biology
- Gene expression regulation
- RNA biology
Background:
- MicroRNAs (miRNAs) are key regulators of gene expression.
- Hyponastic leaves 1 (HYL1), also known as DRB1, is essential for miRNA biogenesis in Arabidopsis thaliana.
- Accurate processing of primary-miRNA (pri-miRNA) by the microprocessor complex requires HYL1 recruitment.
Purpose of the Study:
- To investigate the role of MAP kinase-mediated phosphorylation of AtHYL1.
- To understand the sub-cellular activities and regulation of AtHYL1.
- To elucidate the impact of AtMPK3 on AtHYL1 stability and localization.
Main Methods:
- Investigated AtHYL1 phosphorylation by AtMPK3 in vitro and in vivo.
- Analyzed sub-cellular localization and dimerization of AtHYL1.
- Studied AtHYL1 stability and degradation in wild-type and mpk3 mutant Arabidopsis.
Main Results:
- AtMPK3 phosphorylates AtHYL1 at serine-42, influencing nuclear-cytosolic shuttling.
- AtHYL1 undergoes cleavage by proteases, affecting its sub-cellular activities.
- AtHYL1 dimerization occurs in both nucleus and cytosol; C-terminus regulates stability and localization.
- AtHYL1 is hyper-phosphorylated and more stable in mpk3 mutants, indicating AtMPK3 negatively regulates AtHYL1 stability.
Conclusions:
- AtMPK3 acts as a negative regulator of AtHYL1 protein stability.
- AtMPK3-induced phosphorylation promotes AtHYL1 degradation, impacting miRNA processing.
- Understanding AtHYL1 regulation by phosphorylation provides insights into miRNA biogenesis control.
Related Concept Videos
02:17Microtubule Instability
02:51mRNA Stability and Gene Expression
Cis-acting Elements involved in mRNA stability
01:22MicroRNAs
01:45Destabilization of Microtubules
01:23Regulation of Expression at Multiple Steps
01:53RNA Stability