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キーワード:
Base Sequence
Catalysis
Cell Nucleolus/metabolism
Coiled Bodies/metabolism
Exoribonucleases/genetics/*metabolism
Exosome Multienzyme Ribonuclease Complex
Humans
Nuclear Proteins/metabolism
Nucleotide Motifs
Polyadenylation
Protein Transport
RNA Editing
RNA Nucleotidyltransferases/*metabolism
RNA, Small Nucleolar/*chemistry/*metabolism
要旨:
Small nucleolar and small Cajal body RNAs (snoRNAs and scaRNAs) of the H/ACA box and C/D box type are generated by exonucleolytic shortening of longer precursors. Removal of the last few nucleotides at the 3' end is known to be a distinct step. We report that, in human cells, knock-down of the poly(A) specific ribonuclease (PARN), previously implicated only in mRNA metabolism, causes the accumulation of oligoadenylated processing intermediates of H/ACA box but not C/D box RNAs. In agreement with a role of PARN in snoRNA and scaRNA processing, the enzyme is concentrated in nucleoli and Cajal bodies. Oligo(A) tails are attached to a short stub of intron sequence remaining beyond the mature 3' end of the snoRNAs. The noncanonical poly(A) polymerase PAPD5 is responsible for addition of the oligo(A) tails. We suggest that deadenylation is coupled to clean 3' end trimming, which might serve to enhance snoRNA stability.
