세미나 장소 : K101

세미나 일시 : 2010. 05.20  16:30

세미나 발표자 : University of Copenhagen 양성욱교수

Structure of Arabidopsis HYPONASTIC LEAVES1 and its molecular implications for miRNA processing

The Arabidopsis HYPONASTIC LEVAES1 (HYL1) is a double-stranded RNA-binding protein that forms a complex with DICER-LIKE1 (DCL1) and SERRATE (SE) to facilitate processing of
primary miRNAs (pri-miRNAs) into miRNAs. However, the structural mechanism of miRNA maturation by this complex is poorly understood. Here, we present the crystal structures of doublestranded RNA binding domains (dsRBD1 and dsRBD2) of HYL1 and HYL1 dsRBD1 (HR1)/dsRNA complex. For comparative analysis we also determined the crystal structure of the human TRBP2 dsRBD2 (TR2)/dsRNA complex. Both HR1 and TR2 are canonical dsRBDs for
dsRNA binding and they share almost identical structural features in dsRNA recognition. By contrast, HR2 of HYL1 is a non-canonical dsRBD harboring a dimerization interface. Domain swapping within the context of HYL1 demonstrates that TR2 can supplant the function of HR1 in vitro and in vivo. Further biochemical analyses suggest that HYL1 probably binds to the miRNA/miRNA* region of precursors. Our results indicate that HR1 and HR2 cooperate to bind dsRNA, whereas HR2 may further mediate HYL1 dimerization to enhance binding affinity. We propose a hypothetical model by which HYL1 possibly recognizes the miRNA/miRNA* duplex region of miRNA precursors, together with SE, to facilitate precise and efficient miRNA processing by DCL1.