Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA; Department of Biochemistry, School of Life Sciences, Fudan University, Shanghai 200433, China.
Mol Cell. 2014 Feb 20;53(4):606-16. doi: 10.1016/j.molcel.2014.01.003. Epub 2014 Jan 30.
We have solved two families of crystal structures of the human Dicer "platform-PAZ-connector helix" cassette in complex with small interfering RNAs (siRNAs). The structures possess two adjacently positioned pockets: a 2 nt 3'-overhang-binding pocket within the PAZ domain (3' pocket) and a phosphate-binding pocket within the platform domain (phosphate pocket). One family of complexes contains a knob-like α-helical protrusion, designated "hDicer-specific helix," that separates the two pockets and orients the bound siRNA away from the surface of Dicer, which could be indicative of a product release/transfer state. In the second complex, the helical protrusion is melted/disordered and the bound siRNA is aligned toward the surface of Dicer, suggestive of a cleavage-competent state. These structures allow us to propose that the transition from the cleavage-competent to the postulated product release/transfer state may involve release of the 5'-phosphate from the phosphate pocket while retaining the 3' overhang in the 3' pocket.
我们已经解决了两个家族的人 Dicer“平台-PAZ-连接器螺旋”盒式结构与小干扰 RNA（siRNA）的复合物的晶体结构。这些结构具有两个相邻的口袋：PAZ 结构域内的 2nt 3'-突出结合口袋（3'口袋）和平台结构域内的磷酸结合口袋（磷酸口袋）。一个复合物家族包含一个类似旋钮的α-螺旋突起，称为“hDicer 特异性螺旋”，它将两个口袋分开，并使结合的 siRNA 远离 Dicer 的表面，这可能表明是产物释放/转移状态。在第二个复合物中，螺旋突起融化/无序，结合的 siRNA 向 Dicer 的表面对齐，提示处于切割活性状态。这些结构使我们能够提出，从切割活性到假设的产物释放/转移状态的转变可能涉及从磷酸口袋中释放 5'-磷酸，同时在 3'口袋中保留 3'突出。
