Post-transcriptional regulation of the micro RNA pathway

MANAVELLA PA,

Congreso; LII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2016

MicroRNAs (miRNAs) are small RNA molecules with critical roles during development of multicellular organisms. In plants, these small regulatory molecules are produced from primary miRNA transcripts by a single nuclear enzyme, DICER-LIKE 1 (DCL1). The accurate excision of a miRNA relies on the interaction of DCL1 with its cofactor HYPONASTIC LEAVES1 (HYL1). Once a miRNA is produced it is loaded into an ARGONAUTE (AGO) protein leading the RISC complex to a target mRNA. The miRNAs pathway comprises multiple well-orchestrated steps to ensure the precise and balanced silencing of target genes. In the past years, we have used a large-scale luciferase-based genetic screen, followed by whole-genome sequencing, to identify new co-factors regulating the miRNA production and activity. The analysis of the isolated mutants revealed new and intriguing layers of regulation of the pathway. Among them, we have found that the dephosphorylation of HYL1, by CPL1, is required for full activity of the protein. Such regulation is tightly controlled tissue specifically by RCF3. Lately we also found the biological purpose of the phosphorylated, inactive, reservoir of HYL1 in the cell. In another layer of post-translational regulation, we have identified mutant plants with an impaired AGO1 stability that lead to severe developmental defects caused by an unbalance miRNA-mediated gene silencing.