Biomedical subjects

D Tollervey

Publications and source records attributed to D Tollervey.

101 records · Page 6Linked to original sources

PubMed1989

Two genes encode 7SL RNAs in the yeast Yarrowia lipolytica.

We have identified an abundant cytoplasmic 7S RNA in crude extracts of the yeast Yarrowia lipolytica. A cDNA probe was prepared from this RNA and used to screen a genomic library. The DNA sequence of a positive clone was determined and the end positions of the 7S RNA gene established by comparison with the sequence of the extremities of 7S RNA. This gene, designated SCR2, encodes a 270-nucleotide RNA that can be folded into a secondary structure similar to that of 7SL RNAs. This RNA is 94.4% homologous to a previously identified 7S RNA from this yeast, but is encoded by a separate gene with highly divergent flanking sequences.

Base Sequence↗

PubMed1988

7SL RNA from Schizosaccharomyces pombe is encoded by a single copy essential gene.

We have identified an abundant ribonucleoprotein particle from Schizosaccharomyces pombe with properties related to those of the vertebrate signal recognition particle (SRP), including cytoplasmic localization, association with microsomes and ribosomes at low, but not high, salt concentrations and high resistance to micrococcal nuclease. The 256-nucleotide RNA component carries a 5'-triphosphate group and shows close secondary structure, and limited primary sequence homology to vertebrate 7SL RNA. 7SL-like RNAs were also detected in a number of other fungi. The single copy gene (SRP7) encoding S.pombe 7SL was disrupted by insertion of a transposon carrying the selective marker LEU2, and the disrupted gene was used to replace one chromosomal SRP7 gene in a diploid strain. Haploid srp7[unk] strains fail to germinate.

Journal Article↗

PubMed1988

Characterization of an SNR gene locus in Saccharomyces cerevisiae that specifies both dispensible and essential small nuclear RNAs.

A genetic locus is described that specifies two Saccharomyces cerevisiae small nuclear RNAs (snRNAs). The genes specifying the two snRNAs are separated by only 67 base pairs and are transcribed in the same direction. The product RNAs contain 128 and 190 nucleotides and are designated snR128 and snR190, respectively. These RNAs resemble snRNAs of other eucaryotes in nuclear localization and possession of a 5' trimethylguanosine cap. Neither snRNA is related in sequence to previously described vertebrate or yeast snRNAs. Both RNAs exhibit properties consistent with nucleolar organization and hydrogen bonding to pre-rRNA species, suggesting possible roles in ribosome biogenesis. The snR128 species cosediments with deproteinized 27S pre-rRNA, whereas snR190 is associated with a 20S intermediate. Gene disruption in vitro followed by replacement of the chromosomal alleles reveals that SNR128 is essential, whereas SNR190 is not.

Base Sequence↗

PubMed1987

A yeast small nuclear RNA is required for normal processing of pre-ribosomal RNA.

In Saccharomyces cerevisiae, seven snRNAs (snR3, 4, 5, 8, 9, 10 and 17) are retained in the nucleus under conditions in which nucleoplasmic RNAs are lost, and may be nucleolar. All of these snRNAs show properties consistent with hydrogen bonding to pre-ribosomal RNAs; snR5 and 8 with 20S pre-rRNA, snR3, 4, 10 and 17 with 35S pre-rRNA and snR9 with 20-35S RNA. Strains lacking snR10 are impaired in growth and specifically defective in the processing of 35S RNA. Processing is slowed, leading to 35S RNA accumulation and most cleavage occurs, not at the normal sites, but at sites which in wild-type strains are used for subsequent steps in rRNA maturation.

Molecular Weight↗

PubMed1987

High level of complexity of small nuclear RNAs in fungi and plants.

The complexity of the trimethylguanosine-capped, small nuclear RNA (snRNA) populations in a number of organisms has been examined using immunoprecipitation and two-dimensional gels. From the fungi Aspergillus nidulans and Schizosaccharomyces pombe, over 30 major snRNAs can be resolved. The most abundant of these correspond to the putative analogues of vertebrate U1, U2, U4 and U5, which have been reported to be precipitated by anti-Sm antibodies, but other snRNAs are little less abundant than the major Sm-precipitable species. A similarly high level of complexity of snRNAs is detected in pea plants. In Candida albicans, the snRNAs are somewhat less numerous (about 22 major species) and are substantially less abundant than those of the above fungi, features shared with another budding yeast, Saccharomyces cerevisiae. Ten species of human snRNA have been reported; on two-dimensional gels, a number of additional snRNAs can be resolved from human cells. Each fungus, as well as pea plants, contains snRNAs substantially larger than any reported from vertebrates or detected in the human RNA used here. It appears that many eukaryotes contain substantially more species of snRNA than was previously believed.

Aspergillus nidulans↗

PubMed1987

Fungal small nuclear ribonucleoproteins share properties with plant and vertebrate U-snRNPs.

snRNAs with properties closely related to those of the major vertebrate U-snRNAs are present in the fungi Aspergillus nidulans, Neurospora crassa and Schizosaccharomyces pombe. These RNAs possess a tri-methyl guanosine cap structure and a subset cross-hybridizes with human U1 and U2 clones. In the form of snRNPs, snRNAs from these fungi as well as from Saccharomyces cerevisiae and pea plants are immunoprecipitated by human and anti-Sm or anti-(U1)RNP autoimmune antibodies. On micro-injection into the cytoplasm of Xenopus oocytes, the snRNAs are packaged into ribonucleoprotein particles and migrate into the nucleus. The results demonstrate a hitherto unsuspected degree of evolutionary conservation in snRNA structure, snRNP protein structure, and sites of RNA-protein interaction within snRNPs.

Animals↗

PubMed1985

Deletion of a yeast small nuclear RNA gene impairs growth.

We have cloned and sequenced the single copy gene SNR10 which encodes the yeast small nuclear RNA, snR10. This species does not show obvious primary sequence homology to any previously identified small nuclear RNA. As an inital step towards determining the function of snR10, we have introduced insertions and deletions into the chromosomal copy of the gene. Strains lacking an intact copy of SNR10 are viable but considerably imparied in growth, particularly at elevated osmotic strengths or low temperatures; at 25 degrees C the doubling time of snr10- strains is 47% greater than that of otherwise isogenic SNR10 strains. As judged by the incorporation of radioactive precursors, snr10- strains are impaired in net RNA synthesis at low temperatures. The identification of a leaky, conditional phenotype associated with the deletion of this small nuclear RNA gene was entirely unexpected since the defect in snR10 synthesis is complete and non-conditional.

Base Sequence↗

PubMed1983

Yeast contains small nuclear RNAs encoded by single copy genes.

We have identified a group of RNA molecules in Saccharomyces cerevisiae that appears to be equivalent to the U class of small nuclear RNAs previously described in other eucaryotes, resembling them in size, metabolic stability, 5' cap structure, presence of modified bases, and nuclear localization. However, the yeast snRNAs differ from their counterparts in several potentially important ways. First, they are present in very low abundance, less than 200 copies per cell, as compared to 10(5)-10(6) for mammalian U1-U6. Second, there appear to be more species in yeast than in any cell type previously examined. Finally, we have cloned five yeast snRNA genes, and find that each is present in a single copy per haploid genome, whereas all previously characterized snRNAs are encoded by multiple (5 to 100) gene copies. The presence of single copy genes in yeast will greatly facilitate the genetic analysis of snRNA function.

Base Sequence↗

PubMed1983

A U4-like small nuclear RNA is dispensable in yeast.

We have cloned a single copy gene that encodes a small nuclear RNA, designated snR3, from the yeast Saccharomyces cerevisiae. This RNA is highly conserved among fungi, and sequence and secondary structure analyses suggest that snR3 is analogous to mammalian U4 snRNA. To determine whether snR3 has an essential function in yeast, the gene (designated SNR3), was disrupted by replacing 35 nucleotides of coding sequences with 2.2 kb of yeast DNA containing the LEU2 gene. Since cells entirely lacking snR3 were expected to be inviable, the nonfunctional gene was used to replace one chromosomal copy in a diploid cell, and the diploid transformants were sporulated. Surprisingly, virtually all tetrads gave rise to four viable spores. Moreover, these haploid strains, which have been shown by DNA blot hybridization to lack an intact copy of the SNR3 gene, and which contain no detectable snR3 transcripts, are indistinguishable from their SNR3+ sister spores under a variety of growth conditions.

Alleles↗

PubMedDate not supplied

Genetic and biochemical analyses of yeast RNase MRP.

RNase MRP cleaves the yeast pre-rRNA at a site in internal transcribed spacer 1 (ITS1) and this cleavage can be reproduced in vitro by the highly purified enzyme. Two protein components (Pop1p and Pop2p) have been identified which are common to yeast RNase MRP and RNase P. Moreover, purified RNase P can also cleave the pre-rRNA substrate in vitro, underlining the similarities between these particles. Genetic evidence suggests that RNase MRP functionally interacts with the snoRNPs which are required for other pre-RNA processing reactions.

DNA, Ribosomal↗

PubMedDate not supplied

Trans-acting factors in yeast pre-rRNA and pre-snoRNA processing.

The major intermediates in the pathway of pre-rRNA processing in yeast and other eukaryotes were originally identified by biochemical analyses. However, as a result of the analysis of the effects of mutations in trans-acting factors, the yeast pre-rRNA processing pathway is now characterized in far more detail than that of other eukaryotes. These analyses have led to the identification of processing sites and intermediates that were either too close in size or too short lived to detected by biochemical analyses alone. In addition, it was generally unclear whether pre-rRNA processing steps were endonucleolytic or exonucleolytic; analyses of trans-acting factors is now revealing a complex mixture of endonucleolytic and exonucleolytic processing steps. Many of the small nucleolar RNAs (snoRNAs) are excised from larger precursors. Analyses of trans-acting factors are also revealing details of pre-snoRNA processing in yeast. Interestingly, factors involved in pre-snoRNA processing turn out to be components that also function in pre-rRNA processing, suggesting a potential mechanism for the coregulation of rRNA and snoRNA synthesis. In general, very little is known about the regulation of pre-rRNA processing steps. The best candidate for a system regulating specific pre-rRNA processing reactions has recently been revealed by the analysis of a yeast pre-RNA methylase. Here we will review recent data on the trans-acting factors involved in yeast ribosome synthesis and discuss how these analyses have contributed to our current view of this complex process.

Cell Nucleolus↗