The Protein Phosphatase 4 and SMEK1 Complex Dephosphorylates HYL1 to Promote miRNA Biogenesis by Antagonizing the MAPK Cascade in Arabidopsis

Publication date: 5 June 2017
Source:Developmental Cell, Volume 41, Issue 5
Author(s): Chuanbin Su, Ziwei Li, Jinping Cheng, Lei Li, Songxiao Zhong, Li Liu, Yun Zheng, Binglian Zheng
Phosphorylation plays an essential role in microRNA (miRNA) processing by regulating co-factors of the miRNA biogenesis machinery. HYL1 (Hyponastic Leaves 1), a core co-factor in plant miRNA biogenesis, is a short-lived phosphoprotein. However, the precise balance and regulatory mechanism of the stability and phosphorylation of HYL1 remain unclear. Here, we show that a highly conserved PP4 (Protein Phosphatase 4) and SMEK1 (Suppressor of MEK 1) complex dephosphorylates HYL1 to promote miRNA biogenesis, by antagonizing the MAPK cascade in Arabidopsis. The smek1 mutants exhibit defective miRNA biogenesis due to accelerated degradation of HYL1. SMEK1 stabilizes HYL1 in a dual manner: SMEK1, as a suppressor, inhibits MAPK activation to attenuate HYL1 phosphorylation; SMEK1 assembles a functional PP4 to target HYL1 for dephosphorylation. Moreover, the protein level of SMEK1 is increased in response to abscisic acid. Our results provide insights into the delicate balance between a protein kinase and a phosphatase during miRNA biogenesis.

Teaser

Su et al. show that that a PP4 and SMEK1 complex promotes Arabidopsis miRNA biogenesis by dephosphorylating and stabilizing HYL1 (homolog to animal DGCR8 and TRBP), which promotes miRNA processing accuracy. PP4/SMEK1 is responsive to abscisic acid and antagonizes the MAPK cascade to regulate HYL1 phosphorylation status and protein level.


http://ift.tt/2sSSIRJ