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D A Brow

Publications and source records attributed to D A Brow.

25 records · Page 2Linked to original sources
PubMed1989

Small nuclear RNAs from budding yeasts: phylogenetic comparisons reveal extensive size variation.

Homologues of each of the five metazoan snRNAs required for pre-mRNA splicing have recently been identified in the budding yeast Saccharomyces cerevisiae on the basis of shared structural elements and evidence of similar roles during splicing. However, the spliceosomal snRNAs in this yeast are up to six times larger than their mammalian counterparts, suggesting that they may perform additional, perhaps species-specific, functions in the pre-mRNA processing pathway. We have undertaken a survey of 23 other budding yeasts to determine whether increased snRNA size is unique to Sacch. cerevisiae and, if not, to look for common structural motifs among homologous snRNAs. Our studies reveal that the spliceosomal snRNAs exhibit a surprising degree of size variation among these species. Furthermore, partial sequence analysis has identified a specific domain in the U6 snRNA which accounts for the observed size polymorphisms.

Base Sequence↗
PubMed1988

Spliceosomal RNA U6 is remarkably conserved from yeast to mammals.

The small nuclear RNA U6 and its gene have been isolated from yeast. In striking contrast to other yeast spliceosomal RNAs, U6 is very similar in size, sequence and structure to its mammalian homologue. The single-copy gene is essential. These properties suggest a central role in pre-mRNA processing. An extensive base-pairing interaction with U4 snRNA is described; the destabilization of the U4/U6 complex seen during splicing thus requires a large conformational change.

Base Sequence↗
PubMed1987

Modulation of yeast 5 S rRNA synthesis in vitro by ribosomal protein YL3. A possible regulatory loop.

Synthesis of yeast 5 S rRNA in a homologous cell-free system has previously been shown to be inhibited by exogenous yeast 5 S rRNA. This inhibition is diminished when 5 S rDNA is first incubated with the cell-free system, implying the presence of a transcription factor IIIA analog in yeast, and is dependent on the nucleotide sequence of the 5 S rRNA added. A two-dimensional gel electrophoresis method was used to demonstrate assembly of newly synthesized 5 S rRNA into a ribonucleoprotein complex containing ribosomal protein YL3. Immunodepletion of the cell-free system with anti-YL3 IgG was found to increase the sensitivity of 5 S rRNA synthesis to inhibition by 5 S rRNA. We propose a model for the regulation of yeast 5 S rRNA synthesis in which YL3 competes with the presumptive transcription factor IIIA analog for binding of 5 S rRNA.

Homeostasis↗
PubMed1987

In vitro transcripts of a yeast variant 5 S rRNA gene exhibit alterations in 3'-end processing and protein binding.

When a yeast 5 S rRNA gene with a variant 3'-terminal nucleotide sequence was transcribed in a homologous cell-free system, primary transcripts that were shorter, more heterogeneous in length and much more resistant to processing than pre-5 S rRNA from the major "repeat" 5 S rRNA gene were produced. After 3'-end processing, variant 5 S rRNA was one nucleotide shorter than mature repeat 5 S rRNA and was bound much less strongly to ribosomal protein YL3. The stable variant pre-5 S rRNA appeared to bind another, unidentified protein. The formation of this presumptive ribonucleoprotein complex was disrupted by (Up)4UOH, suggesting that it may contain a yeast analog of the mammalian La protein.

Base Sequence↗
PubMed1987

An essential snRNA from S. cerevisiae has properties predicted for U4, including interaction with a U6-like snRNA.

Three yeast snRNAs (snR20, snR7, and snR14) have been implicated in pre-mRNA splicing. snR20 and snR7 contain domains of homology to U2 and U5, respectively, and each is required for viability. These RNAs are found associated with the spliceosome, as is snR14. We show here that snR14 is also an essential gene product. Sequence analysis reveals that, like snR7 and snR20, snR14 contains a consensus binding site for the Sm antigen, a feature common to all mammalian snRNAs involved in splicing. Moreover, snR14 exhibits several blocks of sequence and structural homology to U4, which in metazoans is found in association with U6. Native gel electrophoresis demonstrates that snR14 is in fact base-paired with another yeast snRNA, designated snR6, which has primary sequence homology to U6. We conclude that snR14 is the yeast analog of U4.

Animal Population Groups↗
PubMed1983

Protection of ribosomal RNA from kethoxal in polyribosomes. Implication of specific sites in ribosome function.

In an attempt to probe the topography of 5 S, 16 S and 23 S RNAs in a functionally engaged ribosome, polysomes were probed using the structure-sensitive, guanine-specific reagent kethoxal. Reactivities of guanine residues at 38 specific ribosomal RNA sites in polysomes were compared with their corresponding reactivities in vacant 70 S ribosomes. No polysome-specific protection was seen for 5 S RNA. In 16 S RNA, positions 530, 693 or 1079, 966, 1338 and 1517 showed protection in polysomes; all of these sites have highly conserved primary and secondary structures, and include several methylated nucleotides. In 23 S RNA, polysome protection is seen at positions 277, 1071, 1475 or 2112, 2116 and 2751. We attribute polysome-specific protection either to direct contact of transfer RNA and/or messenger RNA with the protected sites or to tRNA and/or mRNA-induced changes in ribosome conformation involving the protected sites.

Aldehydes↗