RNase MRP is required for entry of 35S precursor rRNA into the canonical processing pathway

• DOI: 10.1261/rna.1302909
• Publication Date: 2009-05-23T01:55:56Z
• Authors: Lasse Lindahl; Ananth Bommankanti; Xing Li; Lauren Hayden; Adrienne Jones; Miriam Khan; Tolulope Oni; Janice M. Zengel
• Keywords: RNase MRP; RNase PH; RNase H; ribosome biogenesis; Transcription; Ribonuclease III

RNase MRP is a nucleolar RNA–protein enzyme that participates in the processing of rRNA during ribosome biogenesis. Previous experiments suggested makes nonessential cleavage first internal transcribed spacer. Here we report with new temperature-sensitive mutants Saccharomyces cerevisiae show abundance all early intermediates pathway severely reduced upon inactivation MRP. Transcription continues unabated as determined by RNA polymerase run-on transcription, but precursor transcript does not accumulate, and appears to be unstable. Taken together, these observations suggest blocks at sites A0, A1, A2, A3, which turn, prevents from entering canonical (35S > 20S + 27S 18S 25S 5.8S rRNA). Nevertheless, least some site second spacer takes place form an unusual 24S intermediate, suggesting C2 blocked. Furthermore, long made absence activity, only presence Xrn1p (exonuclease 1), required for pathway. We conclude key initiating transcripts, alternative pathway(s) might provide backup production small amounts rRNA.