摘要
Almost all pre-miRNAs in eukaryotic cytoplasm are recognized and processed into double-stranded microRNAs by the endonuclease Dicer protein comprising of multiple domains. As a key player in the small RNA induced gene silencing pathway, the major domains of Dicer are conserved among different species with the exception of the N-terminal components. Human Dicer＇s N-terminal domain has been shown to play an autoinhibitory function of the protein＇s dicing activity. Such an auto-inhibition can be released when the human Dicer protein dimerizes with its partner protein, such as TRBP, PACT through the N-terminal DExH/D （ATPase- helicase） domain. The typical feature of a pre-miRNA contains a terminal loop and a stem duplex, which bind to human Dicer＇s DExH/D （ATPase-helicase） domain and PAZ domain respectively during the dicing reaction. Here, we show that pre-miRNA＇s terminal loop can regulate human Dicer＇s enzymatic activity by interacting with the DExH/D （ATPase-helicase） domain. We found that various editing products of pre-miR-151 by the ADAR1P110 protein, an A-to-I editing enzyme that modifies pre-miRNAs sequence, have different terminal loop structures and different activity regulatory effects on human Dicer. Single particle electron microscopy reconstruction revealed that pre-miRNAs with different terminal loop structures induce human Dicer＇s DExH/D （ATPase-helicase） domain into different conformational states, in correlation with their activity regulatory effects.
Almost all pre-miRNAs in eukaryotic cytoplasm are recognized and processed into double-stranded microRNAs by the endonuclease Dicer protein comprising of multiple domains. As a key player in the small RNA induced gene silencing pathway, the major domains of Dicer are conserved among different species with the exception of the N-terminal components. Human Dicer＇s N-terminal domain has been shown to play an autoinhibitory function of the protein＇s dicing activity. Such an auto-inhibition can be released when the human Dicer protein dimerizes with its partner protein, such as TRBP, PACT through the N-terminal DExH/D （ATPase- helicase） domain. The typical feature of a pre-miRNA contains a terminal loop and a stem duplex, which bind to human Dicer＇s DExH/D （ATPase-helicase） domain and PAZ domain respectively during the dicing reaction. Here, we show that pre-miRNA＇s terminal loop can regulate human Dicer＇s enzymatic activity by interacting with the DExH/D （ATPase-helicase） domain. We found that various editing products of pre-miR-151 by the ADAR1P110 protein, an A-to-I editing enzyme that modifies pre-miRNAs sequence, have different terminal loop structures and different activity regulatory effects on human Dicer. Single particle electron microscopy reconstruction revealed that pre-miRNAs with different terminal loop structures induce human Dicer＇s DExH/D （ATPase-helicase） domain into different conformational states, in correlation with their activity regulatory effects.
