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Diverse mechanisms for spliceosome-mediated 3' end processing of telomerase RNA.

ABSTRACT: The 3' end of Schizosaccharomyces pombe telomerase RNA (SpTER1) is generated by spliceosomal cleavage, a reaction that corresponds to the first step of splicing. The observation that the spliceosome functions in 3' end processing raised questions about the evolutionary origin and conservation of this mechanism. We now present data in support of spliceosomes generating 3' ends of telomerase RNAs in other fungi. Strikingly, the mechanistic basis for restricting spliceosomal splicing to the first transesterification reaction differs substantially among species. Unlike S. pombe, two other fission yeasts rely on hyperstabilization of the U6 snRNA-5' splice site interaction to impede the 2nd step of splicing. In contrast, a non-canonical 5' splice site blocks the second transesterification reaction in Aspergillus species. These results demonstrate a conserved role for spliceosomes functioning in 3' end processing. Divergent mechanisms of uncoupling the two steps of splicing argue for multiple origins of this pathway.

SUBMITTER: Kannan R

PROVIDER: S-EPMC4299874 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Prevalent and distinct spliceosomal 3'-end processing mechanisms for fungal telomerase RNA.

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SMUG1 promotes telomere maintenance through telomerase RNA end-processing

Project description:SMUG1 promotes telomere maintenance through telomerase RNA end-processing

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Human telomerase RNA processing and quality control

Project description:Primary telomerase RNA transcripts are processed into shorter mature forms that assemble into a complex with the catalytic subunit and provide the template for telomerase activity. In diverse fungi telomerase RNA 3â end processing involves a single cleavage reaction by the spliceosome akin to the first step of splicing. Longer forms of human telomerase RNA (hTR) have been reported, but how the mature form of precisely 451 nucleotides is generated is still unknown. We now show that the splicing inhibitor isoginkgetin causes accumulation of long hTR transcripts, but find no evidence for a direct role for splicing in hTR processing. Instead, isoginkgetin mimics the effects of inhibiting the RNA exosome. Depletion of exosome components and accessory factors reveals functions for the cap binding complex (CBC) and the nuclear exosome targeting (NEXT) complex in hTR turnover. Whereas longer transcripts are predominantly degraded, shorter precursor RNAs are oligo-adenylated by TRF4-2 and either processed by poly (A) specific ribonuclease (PARN) or degraded by the exosome. Our results reveal that hTR biogenesis involves a kinetic competition between RNA processing and quality control pathways and suggest new treatment options for dyskeratosis congenita caused by mutations in RNA processing factors. We cloned and sequenced 3â ends by RLM-RACE coupled with high-throughput sequencing to gain further insights into hTR processing.

2015-11-25 | E-GEOD-73776 | biostudies-arrayexpress

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Human telomerase RNA processing and quality control

2015-11-25 | GSE72055 | GEO

Human telomerase RNA processing and quality control

Project description:Primary telomerase RNA transcripts are processed into shorter mature forms that assemble into a complex with the catalytic subunit and provide the template for telomerase activity. In diverse fungi telomerase RNA 3’ end processing involves a single cleavage reaction by the spliceosome akin to the first step of splicing. Longer forms of human telomerase RNA (hTR) have been reported, but how the mature form of precisely 451 nucleotides is generated is still unknown. We now show that the splicing inhibitor isoginkgetin causes accumulation of long hTR transcripts, but find no evidence for a direct role for splicing in hTR processing. Instead, isoginkgetin mimics the effects of inhibiting the RNA exosome. Depletion of exosome components and accessory factors reveals functions for the cap binding complex (CBC) and the nuclear exosome targeting (NEXT) complex in hTR turnover. Whereas longer transcripts are predominantly degraded, shorter precursor RNAs are oligo-adenylated by TRF4-2 and either processed by poly (A) specific ribonuclease (PARN) or degraded by the exosome. Our results reveal that hTR biogenesis involves a kinetic competition between RNA processing and quality control pathways and suggest new treatment options for dyskeratosis congenita caused by mutations in RNA processing factors.

2015-11-25 | GSE73776 | GEO

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