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General Comment |
Laneve P, et al 2003 reported the purification, cloning and characterization of XendoU, a novel endoribonuclease involved in processing of intron-encoded small nucleolar RNAs in Xenopus laevis.
Such an activity has never been reported before and has several uncommon features that make it quite a novel enzyme: it is poly-U specific, it requires Mn(2+) ions and it produces molecules with 2-3cyclic phosphate termini. Even if XendoU cleaves U-stretches, it displays some preferential cleavage on snoRNA precursor molecules. XendoU also participates in the biosynthesis of another intron-encoded snoRNA, U86, that is contained in the NOP56 gene of X.laevis. A common feature of these snoRNAs is that their production is alternative to that of the mRNA, suggesting an important regulatory role for all the factors involved in the processing reaction.
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