Dynamic regulation of HYL1 provides new insights into its multifaceted role in Arabidopsis

Abstract

15MicroRNAs (miRNAs) are 21 to 24 nucleotide non-coding RNAs that regulate gene 16 expression. Biogenesis of miRNAs is fine-tuned by specialized microprocessor complex, the 17 regulation of which is being continuously understood. Recruitment of HYL1 to the 18 microprocessor complex is crucial for accurate primary-miRNA (pri-miRNA) processing and 19 accumulation of mature miRNA in Arabidopsis thaliana. HYL1 is a double-stranded RNA 20 binding protein also termed as DRB1, has two double-stranded RNA binding domain at N-21 terminal and a highly disordered C-terminal region. Also, the biological activity of HYL1 is 22 dynamically regulated through transition from hyperphosphorylation to hypophosphorylation 23 state. HYL1 is known to be phosphorylated by a MAP kinase MPK3 and SnRK2. However, 24 the precise role of its phosphorylation are still unknown. Recently, the stability of HYL1 25 protein has been shown to be regulated by an unknown protease X. However, the identity of 26 the protease and its molecular mechanisms are poorly understood. Here, we describe, three 27 functionally important facets of HYL1, which provide a better picture of its association with 28 molecular processes. First, we identified a conserved MPK3 phosphorylation site on HYL1 29 and its possible role in the miRNA biogenesis. Secondly, the C-terminal region of HYL1 30 displays tendencies to bind dsDNA. Lastly, the role of C-terminal region of HYL1 in the 31 regulation of its protein stability and the regulation of miRNA biogenesis is documented. We 32 show the unexplored role of C-terminal and hypothesize the novel functions of HYL1 in 33 addition to miRNA biogenesis. We anticipate that the data presented in this study, will open a 34 new dimension of understanding the role of double stranded RNA binding proteins in diverse 35 biological processes of plants and animal.36

Hyponastic Leaves 1 Interacts with RNA Pol II to Ensure Proper Transcription of MicroRNA Genes

“…More importantly, the phosphorylation status of HYL1 could be a factor that distinguishes its roles in transcription and in the processing of pri-miRNAs. An alternative model suggests that the C-terminal region of HYL1, which displays a tendency to bind dsDNA, may interact with chromatin ( Bhagat et al. 2018 ).…”