The U3 small nucleolar ribonucleoprotein functions in the first step of preribosomal RNA processing.
The first cleavage in mammalian pre-rRNA maturation occurs near the 5' end within the 5' external transcribed spacer. Using mouse cell extracts, we show that this processing is abolished by micrococcal nuclease pretreatment. Autoantibodies that recognize the U3, U8, and U13 snRNPs (anti-fibrillarin) deplete processing activity from the extract and selectively immunoprecipitate both rRNA substrates and processing products from the reaction. Specific involvement of the U3 snRNP is demonstrated by native gel electrophoresis of the processing reaction followed by Northern blotting and by oligonucleotide-directed RNAase H abolition of processing activity. Our identification of U3 function is discussed with respect to the molecular basis of pre-rRNA recognition by the U3 snRNP, possible roles of U3 and other nucleolar snRNPs in rRNA processing, and the morphological organization of the nucleolus and the ribosomal transcription complex.
Kass
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Human Genetics Program, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Tyc
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Steitz
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Sollner-Webb
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B
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism; D002466:Cell Nucleolus / Q000378:metabolism*; D004275:DNA, Ribosomal / Q000235:genetics; D004722:Endoribonucleases; D051379:Mice; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D015345:Oligonucleotide Probes; D012322:RNA Precursors / Q000235:genetics*; D012323:RNA Processing, Post-Transcriptional; D012342:RNA, Small Nuclear / Q000235:genetics*; D016914:Ribonuclease H; D012261:Ribonucleoproteins / Q000378:metabolism*; D017411:Ribonucleoproteins, Small Nuclear; D013698:Templates, Genetic
D004275:DNA, Ribosomal; D015345:Oligonucleotide Probes; D012322:RNA Precursors; D012342:RNA, Small Nuclear; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear; D004722:Endoribonucleases; D016914:Ribonuclease H