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miRNAs are a group of small noncoding RNAs that are widely present in eukaryotes. miRNAs are loaded into AGO proteins to form RNA-induced silencing complexes (RISCs) to repress gene expression through target cleavage and/or translational repression. In metazoan miRNAs target more than 50% transcripts. Similarly in plants, they regulate essentially every aspect of growth and development as well as biotic and abiotic stress responses. Therefore, precise control of miRNA production and fine-tuning of homeostasis of miRNA accumulation warrants the functional accuracy and targeting efficacy of miRNAs. miRNAs originate from primary transcripts (pri-miRNAs), which feature stem-loop structures. The pri-miRNAs are sequentially cleaved by Microprocessor that minimally consists of Dicer-like 1 (DCL1), a double-stranded (ds)RNA-binding protein, Hyponastic leaves 1(HYL1), and Serrate (SE) to eventually produce miRNA. In the past years, our lab has extensively studied functions and mechanisms of SE protein in miRNA biogenesis. To our surprise, we have discovered that SE is a scaffold protein that functions at the interface between microprocessor and epigenetic machinery that includes SWI2/SNF2 chromatin remodel factors and histone methyltransferases. Moreover, the accumulation of SE protein itself is also tightly controlled through 20S proteasome to survey proper RNA metabolism. In my seminar, we will learn about SE-centered regulatory network in multiple molecular processes.