PRP4KA phosphorylates SERRATE for degradation via 20S proteasome to fine-tune miRNA production in Arabidopsis.

Phosphorylation can quickly switch on/off protein functions. Here, we reported pre-mRNA processing 4 kinase A (PRP4KA), and its paralogs interact with Serrate (SE), a key factor in RNA processing. PRP4KA phosphorylates at least five residues of SE in vitro and in vivo. Hypophosphorylated, but not hyperphosphorylated, SE variants could readily rescue se phenotypes in vivo. Moreover, hypophosphorylated SE variants had stronger binding affinity to microprocessor component HYL1 and were more resistant to degradation by 20S proteasome than hyperphosphorylated counterparts. Knockdown of the kinases enhanced the accumulation of hypophosphorylated SE. However, the excessive SE interfered with the assembly and function of SE-scaffolded macromolecule complexes, causing the se-like defects in the mutant and wild-type backgrounds. Thus, phosphorylation of SE via PRP4KA can quickly clear accumulated SE to secure its proper amount. This study provides new insight into how protein phosphorylation regulates miRNA metabolism through controlling homeostasis of SE accumulation in plants.

Citation

Lin Wang, Xingxing Yan, Yanjun Li, Zhiye Wang, Shweta Chhajed, Baoshuan Shang, Zhen Wang, Suk Won Choi, Hongwei Zhao, Sixue Chen, Xiuren Zhang. PRP4KA phosphorylates SERRATE for degradation via 20S proteasome to fine-tune miRNA production in Arabidopsis. Science advances. 2022 Mar 25;8(12):eabm8435

PMID: 35333566

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