The 5′ end of the 18S rRNA can be positioned from within the mature rRNA

Sharma, Kishor; Venema, Jaap; Tollervey, David

doi:10.1017/s1355838299990052

Cited by 17 publications

(18 citation statements)

References 16 publications

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“…Several other mutations tested in the 18S stem-loop structure all prevented the synthesis of functional ribosomes (32). This region of the ribosome is highly conserved in evolution (2), and it appears that changes are poorly tolerated.…”

Section: Resultsmentioning

confidence: 99%

“…2). The positioning of site A 1 is determined with respect to two signals: the sequence 5Ј to the site of cleavage and the 5Ј stem loop within the 18S rRNA (32,39). The insertion of two U residues immediately 5Ј to the stem allows the contribution made by each of these signals to the positioning of the cleavage site to be resolved (39).…”

Section: Resultsmentioning

confidence: 99%

“…The site of A 1 cleavage is positioned with respect to both the 5Ј flanking sequence and the stem loop within the 18S rRNA (32,39). The contributions made by these two signals can be resolved by the insertion 5Ј to the stem of two uracil residues (32,39), which are present in the sub5 and sub6 pre-rRNAs ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The contributions made by these two signals can be resolved by the insertion 5Ј to the stem of two uracil residues (32,39), which are present in the sub5 and sub6 pre-rRNAs ( Fig. 2A).…”

Section: Resultsmentioning

confidence: 99%

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Base Pairing between U3 Small Nucleolar RNA and the 5′ End of 18S rRNA Is Required for Pre-rRNA Processing

Sharma

Tollervey

1999

Molecular and Cellular Biology

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The loop of a stem structure close to the 5 end of the 18S rRNA is complementary to the box A region of the U3 small nucleolar RNA (snoRNA). Substitution of the 18S loop nucleotides inhibited pre-rRNA cleavage at site A 1 , the 5 end of the 18S rRNA, and at site A 2 , located 1.9 kb away in internal transcribed spacer 1. This inhibition was largely suppressed by a compensatory mutation in U3, demonstrating functional base pairing. The U3-pre-rRNA base pairing is incompatible with the structure that forms in the mature 18S rRNA and may prevent premature folding of the pre-rRNA. In the Escherichia coli pre-rRNA the homologous region of the 16S rRNA is also sequestered, in that case by base pairing to the 5 external transcribed spacer (5 ETS). Cleavage at site A 0 in the yeast 5 ETS strictly requires base pairing between U3 and a sequence within the 5 ETS. In contrast, the U3-18S interaction is not required for A 0 cleavage. U3 therefore carries out at least two functionally distinct base pair interactions with the pre-rRNA. The nucleotide at the site of A 1 cleavage was shown to be specified by two distinct signals; one of these is the stem-loop structure within the 18S rRNA. However, in contrast to the efficiency of cleavage, the position of A 1 cleavage is not dependent on the U3-loop interaction. We conclude that the 18S stem-loop structure is recognized at least twice during pre-rRNA processing.Eukaryotic nucleoli contain a large number of small nucleolar RNA (snoRNA) species, most of which function as guides for rRNA modifications. However, a small number of snoRNAs are required for processing of the pre-rRNA (reviewed in references 21 and 36), of which the most studied is U3. Genetic depletion of U3 in the yeast Saccharomyces cerevisiae inhibits three early pre-rRNA cleavage reactions on the pathway of 18S rRNA synthesis (Fig. 1); cleavage is inhibited at sites A 0 (in the 5Ј external transcribed spacer [5Ј ETS]), A 1 (the 5Ј end of the mature 18S rRNA), and A 2 (in internal transcribed spacer 1 [ITS1]) (14). In contrast, the cleavage of site A 3 and sites further in the 3Ј direction on the pathway of 5.8S and 25S synthesis is unaffected by depletion of U3. Depletion of the U3-associated proteins Nop1p, Sof1p, and Mpp10p leads to essentially identical phenotypes (8,15,37), indicating that the intact U3 small nucleolar ribonucleoprotein (snoRNP) particle is required for pre-rRNA cleavage at these sites. Depletion of U3 has also been reported to inhibit in vitro cleavage of the mouse 5Ј ETS (16) and pre-rRNA processing in Xenopus oocytes (5, 30).In vivo psoralen cross-linking experiments identified several sites of interaction between the yeast U3 snoRNA and the pre-rRNA. One was a single-stranded region in the 5Ј region of the U3 snoRNA (nucleotides [nt] 39 to 48) which exhibited a 10-nt complementarity to a region of the 5Ј ETS (nt 470 to 479; approximately 140 nt 5Ј to site A 0 and 230 nt 5Ј to site A 1 ) (3, 4). Disruption of this base pairing blocked cleavage at sites A 0 , A 1 , and A 2 and accumulation ...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…The contributions made by these two signals can be resolved by the insertion 5Ј to the stem of two uracil residues (32,39), which are present in the sub5 and sub6 pre-rRNAs ( Fig. 2A).…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Base Pairing between U3 Small Nucleolar RNA and the 5′ End of 18S rRNA Is Required for Pre-rRNA Processing

Sharma

Tollervey

1999

Molecular and Cellular Biology

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126

140

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“…In yeast, 2 signals define the position of the mature 18S rRNA 5 0 -end: the first one is the 5 0 -ETS sequence immediately upstream of the A 1 cleavage site, while the second one is a stem of a central pseudoknot structure within 18S rRNA with 3 nucleotides separating the A 1 site from this stem. 38,63 The conservation of 5 0 -ETS sequence preceding A 1 is observed in Ascomycete fungi and among plants, but does not exist in vertebrates, suggesting that only the second mechanism of A 1 site positioning mentioned above may operate in the latter, including humans. This may also influence the difference in phenotypes observed in yeast and human cells upon inactivation of yUtp24 and hUTP24, respectively.…”

Section: 62mentioning

confidence: 99%

hUTP24 is essential for processing of the human rRNA precursor at site A₁, but not at site A₀

et al. 2015

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Production of ribosomes relies on more than 200 accessory factors to ensure the proper sequence of steps and faultless assembly of ribonucleoprotein machinery. Among trans-acting factors are numerous enzymes, including ribonucleases responsible for processing the large rRNA precursor synthesized by RNA polymerase I that encompasses sequences corresponding to mature 18S, 5.8S, and 25/28S rRNA. In humans, the identity of most enzymes responsible for individual processing steps, including endoribonucleases that cleave pre-rRNA at specific sites within regions flanking and separating mature rRNA, remains largely unknown. Here, we investigated the role of hUTP24 in rRNA maturation in human cells. hUTP24 is a human homolog of the Saccharomyces cerevisiae putative PIN domaincontaining endoribonuclease Utp24 (yUtp24), which was suggested to participate in the U3 snoRNA-dependent processing of yeast pre-rRNA at sites A 0 , A 1 , and A 2 . We demonstrate that hUTP24 interacts to some extent with proteins homologous to the components of the yeast small subunit (SSU) processome. Moreover, mutation in the putative catalytic site of hUTP24 results in slowed growth of cells and reduced metabolic activity. These effects are associated with a defect in biogenesis of the 40S ribosomal subunit, which results from decreased amounts of 18S rRNA as a consequence of inaccurate pre-rRNA processing at the 5 0 -end of the 18S rRNA segment (site A 1 ). Interestingly, and in contrast to yeast, site A 0 located upstream of A 1 is efficiently processed upon UTP24 dysfunction. Finally, hUTP24 inactivation leads to aberrant processing of 18S rRNA 2 nucleotides downstream of the normal A 1 cleavage site.

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Cotranscriptional events in eukaryotic ribosome synthesis

2014

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Eukaryotic ribosomes are synthesized in a complex, multistep pathway. This begins with transcription of the rDNA genes by a specialized RNA polymerase, accompanied by the cotranscriptional binding of large numbers of ribosome synthesis factors, small nucleolar RNAs and ribosomal proteins. Cleavage of the nascent transcript releases the early pre-40S and pre-60S particles, which acquire export competence in the nucleoplasm prior to translocation through the nuclear pore complexes and final maturation to functional ribosomal subunits in the cytoplasm. This review will focus on the many and complex interactions occurring during pre-rRNA synthesis, particularly in budding yeast in which the pathway is best understood.

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The 5′ end of the 18S rRNA can be positioned from within the mature rRNA

Cited by 17 publications

References 16 publications

Base Pairing between U3 Small Nucleolar RNA and the 5′ End of 18S rRNA Is Required for Pre-rRNA Processing

Base Pairing between U3 Small Nucleolar RNA and the 5′ End of 18S rRNA Is Required for Pre-rRNA Processing

hUTP24 is essential for processing of the human rRNA precursor at site A₁, but not at site A₀

Cotranscriptional events in eukaryotic ribosome synthesis

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The 5′ end of the 18S rRNA can be positioned from within the mature rRNA

Cited by 17 publications

References 16 publications

Base Pairing between U3 Small Nucleolar RNA and the 5′ End of 18S rRNA Is Required for Pre-rRNA Processing

Base Pairing between U3 Small Nucleolar RNA and the 5′ End of 18S rRNA Is Required for Pre-rRNA Processing

hUTP24 is essential for processing of the human rRNA precursor at site A1, but not at site A0

Cotranscriptional events in eukaryotic ribosome synthesis

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hUTP24 is essential for processing of the human rRNA precursor at site A₁, but not at site A₀