A long form (tRNase ZL) of tRNA 3′ processing endoribonuclease (tRNase Z, or 3′ tRNase) can cleave any target RNA at any desired site under the direction of artificial small guide RNA (sgRNA) that mimics a 5′-half portion of tRNA. Based on this enzymatic property, a gene silencing technology has been developed, in which a specific mRNA level can be downregulated by introducing into cells a synthetic 5′-half-tRNA that is designed to form a pre-tRNA-like complex with a part of the mRNA. Recently 5′-half-tRNA fragments have been reported to exist stably in various types of cells, although little is know about their physiological roles. We were curious to know if endogenous 5′-half-tRNA works as sgRNA for tRNase ZL in the cells. Here we show that human cytosolic tRNase ZL modulates gene expression through 5′-half-tRNA. We found that 5′-half-tRNAGlu, which co-immunoprecipitates with tRNase ZL, exists predominantly in the cytoplasm, functions as sgRNA in vitro, and downregulates the level of a luciferase mRNA containing its target sequence in human kidney 293 cells. We also demonstrated that the PPM1F mRNA is one of the genuine targets of tRNase ZL guided by 5′-half-tRNAGlu. Furthermore, the DNA microarray data suggested that tRNase ZL is likely to be involved in the p53 signaling pathway and apoptosis.
Damnacanthal is identified as an effective inhibitor of LIM-kinase. It inhibits chemotaxis of T-cells and migration and invasion of breast carcinoma cells in culture and hapten-induced migration of epidermal Langerhans cells in mouse ears. Damnacanthal is a useful tool for investigating the cellular and physiological functions of LIM-kinase.
Edited by Tamas Dalmay
Keywords:A long form of tRNase Z TRUE gene silencing Small guide RNA MicroRNA Non-coding RNA RNA-induced silencing complex a b s t r a c t A long form of tRNase Z (tRNase Z L ) can cleave any target RNA at any desired site under the direction of artificial small guide RNA including $25-nucleotide hook-shaped RNA. Here we show that human miR-103 can form a hook structure to guide target RNA cleavage by human cytosolic tRNase Z L in vitro. In vivo analyses using luciferase mRNAs modified to contain miR-103 target sequences in their 3 0 untranslated regions indicated that miR-103 downregulates gene expression through directing mRNA cleavage by tRNase Z L . The present data suggest the possibility that human cytosolic tRNase Z L modulates gene expression through a subset of microRNAs in the cells.
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