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MicroRNAs are small RNAs involved in regulation of cognate mRNAs, but predicting their exact targets has been difficult. Using a cross-linking immunoprecipitation technique, a comprehensive examination of endogenous mRNA target sites associated with the C. elegans Argonaute family member ALG-1 is now presented.
The Sec3 subunit of the yeast exocyst complex tethers secretory vesicles to the plasma membrane for exocytosis through interactions with a small GTPase and PtdIns(4,5)P2 in the target membrane. A new study describes the crystal structure of the N-terminal Rho1/Cdc42- and PtdIns(4,5)P2-binding domain of Sec3 in complex with Rho1.
Argonaute family members are key effectors of small RNA function. Predicted structural analogies to allosterically-regulated bacterial ligand-binding proteins, followed by biochemical analysis of the binding properties of Argonautes, now indicate functional allostery between two distinct binding sites that would promote a functional outcome when both a miRNA and capped mRNA are present.
APOBEC3 cytidine deaminases have been implicated in restriction of retroviruses and retrotransposons in mammalian cells. Now human APOBEC3A is shown to be upregulated by interferon and to catalyze the deamination of foreign double-stranded DNA transfected into primary cells or cell lines, with no detectable effect on genomic DNA.