scholarly journals A Novel Model for the RNase MRP-Induced Switch Between Different Forms of 5.8S rRNA

2021 ◽  
Author(s):  
Xiao Li ◽  
Janice M Zengel ◽  
Lasse Lindahl
Keyword(s):  
Rna Polymerase ◽  
18S Rrna ◽  
Rna Polymerase I ◽  
Published Data ◽  
Primary Transcript ◽  
Rna Molecules ◽  
Rnase Mrp ◽  
5.8S Rrna ◽  
Polymerase I ◽  
Novel Model

Processing of the RNA polymerase I pre-rRNA transcript into the mature 18S, 5.8S, and 25S rRNAs requires removing the “spacer” sequences. The canonical pathway for the removal of the ITS1 spacer, located between 18S and 5.8S rRNAs in the primary transcript, involves cleavages at the 3’ end of 18S rRNA and at two sites inside ITS1. The process generates a long and a short 5.8S rRNA that differ in the number of ITS1 nucleotides retained at the 5.8S 5’ end. Here we document a novel pathway that generates the long 5.8S for ITS1 while bypassing cleavage within ITS1. It entails a single endonuclease cut at the 3’-end of 18S rRNA followed by exonuclease Xrn1 degradation of ITS1. Mutations in RNase MRP increase the accumulation of long relative to short 5.8S rRNA; traditionally this is attributed to a decreased rate of RNase MRP cleavage at its target in ITS1, called A3. In contrast, we report here that the MRP induced switch between long and short 5.8S rRNA formation occurs even when the A3 site is deleted. Based on this and our published data, we propose that the switch may depend on RNase MRP processing RNA molecules other than pre-rRNA.

scholarly journals A Novel Model for the RNase MRP-Induced Switch between the Formation of Different Forms of 5.8S rRNA

2021 ◽  
Vol 22 (13) ◽  
pp. 6690
Author(s):  
Xiao Li ◽  
Janice M. Zengel ◽  
Lasse Lindahl
Keyword(s):  
Rna Polymerase ◽  
18S Rrna ◽  
Canonical Pathway ◽  
Rna Polymerase I ◽  
Published Data ◽  
Rna Molecules ◽  
Rnase Mrp ◽  
5.8S Rrna ◽  
Polymerase I ◽  
Novel Model

Processing of the RNA polymerase I pre-rRNA transcript into the mature 18S, 5.8S, and 25S rRNAs requires removing the “spacer” sequences. The canonical pathway for the removal of the ITS1 spacer involves cleavages at the 3′ end of 18S rRNA and at two sites inside ITS1. The process can generate either a long or a short 5.8S rRNA that differs in the number of ITS1 nucleotides retained at the 5.8S 5′ end. Here we document a novel pathway to the long 5.8S, which bypasses cleavage within ITS1. Instead, the entire ITS1 is degraded from its 5′ end by exonuclease Xrn1. Mutations in RNase MRP increase the accumulation of long relative to short 5.8S rRNA. Traditionally this is attributed to a decreased rate of RNase MRP cleavage at its target in ITS1, called A3. However, results from this work show that the MRP-induced switch between long and short 5.8S rRNA formation occurs even when the A3 site is deleted. Based on this and our published data, we propose that the link between RNase MRP and 5.8S 5′ end formation involves RNase MRP cleavage at unknown sites elsewhere in pre-rRNA or in RNA molecules other than pre-rRNA.

scholarly journals Co-surveillance of ribosomal RNA by the exosome complex and nucleolar RNAi in C. elegans

2020 ◽  
Author(s):  
Shimiao Liao ◽  
Xiangyang Chen ◽  
Ting Xu ◽  
Qile Jin ◽  
Zongxiu Xu ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Rna Degradation ◽  
Rna Polymerase I ◽  
C Elegans ◽  
Small Regulatory Rnas ◽  
Regulatory Rnas ◽  
Rna Exosome ◽  
Polymerase I ◽  
Nuclear Rnai ◽  
Novel Model

AbstractEukaryotic cells express a wide variety of endogenous small regulatory RNAs that function in the nucleus. We previously found that erroneous rRNAs induce the generation of antisense ribosomal siRNAs (risiRNAs) which silence the expression of rRNAs via the nuclear RNAi defective (Nrde) pathway. To further understand the biological roles and mechanisms of this class of small regulatory RNAs, we conducted forward genetic screening to identify factors involved in risiRNA generation in Caenorhabditis elegans. We found that risiRNAs accumulated in the RNA exosome mutants. risiRNAs directed a NRDE-dependent silencing of pre-rRNAs in the nucleolus. In the presence of risiRNA, NRDE-2 accumulated in the nucleolus and colocalized with RNA polymerase I. risiRNA inhibited the transcription elongation of RNA polymerase I by decreasing RNAP I occupancy downstream of the site of RNAi. Meanwhile, exosome mislocalized from the nucleolus to nucleoplasm in suppressor of siRNA (susi) mutants, in which erroneous rRNAs accumulated. These results establish a novel model of rRNA surveillance by combining ribonuclease-mediated RNA degradation with small RNA-directed nucleolar RNAi system.

RNA Polymerase I-Mediated Expression of Influenza Viral RNA Molecules

Virology ◽  
1994 ◽  
Vol 202 (1) ◽  
pp. 477-479 ◽  
Author(s):  
Gabriele Neumann ◽  
Alexandra Zobel ◽  
Gerd Hobom
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase I ◽  
Viral Rna ◽  
Rna Molecules ◽  
Polymerase I

scholarly journals New Model for the Yeast RNA Polymerase I Transcription Cycle

2001 ◽  
Vol 21 (15) ◽  
pp. 4847-4855 ◽  
Author(s):  
Pavel Aprikian ◽  
Beth Moorefield ◽  
Ronald H. Reeder
Keyword(s):  
Rna Polymerase ◽  
Transcription Initiation ◽  
Polymerase Activity ◽  
Rna Polymerase I ◽  
Rrna Synthesis ◽  
New Model ◽  
Pol I ◽  
Stable Association ◽  
Polymerase I ◽  
Novel Model

ABSTRACT Using an immobilized template assay, we observed two steps in assembly of the yeast RNA polymerase I (Pol I) preinitiation complex: stable binding of upstream activating factor (UAF) followed by recruitment of Pol I-Rrn3p and core factor (CF). Pol I is required for stable association of CF with the promoter and can be recruited in the absence of Rrn3p. Upon transcription initiation, Pol I-Rrn3p and CF dissociate from the promoter while UAF remains behind. These findings support a novel model in which the Pol I basal machinery cycles on and off the promoter with each round of transcription. This model accounts for previous observations that rRNA synthesis may be controlled by regulating both promoter accessibility and polymerase activity.

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