Dataset Information

Polyadenylation of ribosomal RNA in human cells.

ABSTRACT: The addition of poly(A)-tails to RNA is a process common to almost all organisms. In eukaryotes, stable poly(A)-tails, important for mRNA stability and translation initiation, are added to the 3' ends of most nuclear-encoded mRNAs, but not to rRNAs. Contrarily, in prokaryotes and organelles, polyadenylation stimulates RNA degradation. Recently, polyadenylation of nuclear-encoded transcripts in yeast was reported to promote RNA degradation, demonstrating that polyadenylation can play a double-edged role for RNA of nuclear origin. Here we asked whether in human cells ribosomal RNA can undergo polyadenylation. Using both molecular and bioinformatic approaches, we detected non-abundant polyadenylated transcripts of the 18S and 28S rRNAs. Interestingly, many of the post-transcriptionally added tails were composed of heteropolymeric poly(A)-rich sequences containing the other nucleotides in addition to adenosine. These polyadenylated RNA fragments are most likely degradation intermediates, as primer extension (PE) analysis revealed the presence of distal fragmented molecules, some of which matched the polyadenylation sites of the proximal cleavage products revealed by oligo(dT) and circled RT-PCR. These results suggest the presence of a mechanism to degrade ribosomal RNAs in human cells, that possibly initiates with endonucleolytic cleavages and involves the addition of poly(A) or poly(A)-rich tails to truncated transcripts, similar to that which operates in prokaryotes and organelles.

SUBMITTER: Slomovic S

PROVIDER: S-EPMC1474067 | biostudies-literature | 2006

REPOSITORIES: biostudies-literature

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Polyadenylation of ribosomal RNA in human cells.

Slomovic Shimyn S Laufer David D Geiger Dan D Schuster Gadi G

Nucleic acids research 20060531 10

The addition of poly(A)-tails to RNA is a process common to almost all organisms. In eukaryotes, stable poly(A)-tails, important for mRNA stability and translation initiation, are added to the 3' ends of most nuclear-encoded mRNAs, but not to rRNAs. Contrarily, in prokaryotes and organelles, polyadenylation stimulates RNA degradation. Recently, polyadenylation of nuclear-encoded transcripts in yeast was reported to promote RNA degradation, demonstrating that polyadenylation can play a double-edg ...[more]

PMID: 16738135

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Project description:Cohesin is a protein complex known for its essential role in chromosome segregation. However, cohesin and associated factors have additional functions in transcription, DNA damage repair, and chromosome condensation. The human cohesinopathy diseases are thought to stem not from defects in chromosome segregation but from gene expression. The role of cohesin in gene expression is not well understood. We used budding yeast strains bearing mutations analogous to the human cohesinopathy disease alleles under control of their native promoter to study gene expression. These mutations do not significantly affect chromosome segregation. Transcriptional profiling reveals that many targets of the transcriptional activator Gcn4 are induced in the eco1-W216G mutant background. The upregulation of Gcn4 was observed in many cohesin mutants, and this observation suggested protein translation was reduced. We demonstrate that the cohesinopathy mutations eco1-W216G and smc1-Q843? are associated with defects in ribosome biogenesis and a reduction in the actively translating fraction of ribosomes, eiF2?-phosphorylation, and (35)S-methionine incorporation, all of which indicate a deficit in protein translation. Metabolic labeling shows that the eco1-W216G and smc1-Q843? mutants produce less ribosomal RNA, which is expected to constrain ribosome biogenesis. Further analysis shows that the production of rRNA from an individual repeat is reduced while copy number remains unchanged. Similar defects in rRNA production and protein translation are observed in a human Roberts syndrome cell line. In addition, cohesion is defective specifically at the rDNA locus in the eco1-W216G mutant, as has been previously reported for Roberts syndrome. Collectively, our data suggest that cohesin proteins normally facilitate production of ribosomal RNA and protein translation, and this is one way they can influence gene expression. Reduced translational capacity could contribute to the human cohesinopathies.

Dataset Information

Polyadenylation of ribosomal RNA in human cells.

Publications

Polyadenylation of ribosomal RNA in human cells.

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