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F Stutz

Publications and source records attributed to F Stutz.

27 records · Page 2Linked to original sources
PubMed1993

U1 small nuclear ribonucleoprotein particle-protein interactions are revealed in Saccharomyces cerevisiae by in vivo competition assays.

Two highly conserved regions of the 586-nucleotide yeast (Saccharomyces cerevisiae) U1 small nuclear RNA (snRNA) can be mutated or deleted with little or no effect on growth rate: the universally conserved loop II (corresponding to the metazoan A loop) and the yeast core region (X. Liao, L. Kretzner, B. Séraphin, and M. Rosbash, Genes Dev. 4:1766-1774, 1990). To examine the contribution of these regions to U1 small nuclear ribonucleoprotein particle (snRNP) activity, a competitor U1 gene, encoding a nonfunctional U1 snRNA molecule, was introduced into a number of strains carrying a U1 snRNA gene with loop II or yeast core mutations. The presence of the nonfunctional U1 gene lowered the growth rate of these mutant strains but not wild-type strains, consistent with the notion that mutant U1 RNAs are less active than wild-type U1 snRNAs. A detailed analysis of the U1 snRNA levels and half-lives in a number of merodiploid strains suggests that these mutant U1 snRNAs interact with U1 snRNP proteins less well than do their wild-type counterparts. Competition for protein factors during snRNP assembly could account for a number of previous observations in both yeast and mammalian cells.

Base Sequence↗
PubMed1992

Defects in mRNA 3'-end formation, transcription initiation, and mRNA transport associated with the yeast mutation prp20: possible coupling of mRNA processing and chromatin structure.

A temperature-sensitive lethal mutation in Saccharomyces cerevisiae, prp20-1, causes defects in several different steps in mRNA metabolism, including mRNA 3'-end formation, transcription initiation, and mRNA transport. Previous work has demonstrated that prp20 mutants are defective in actin pre-mRNA splicing. PRP20 is related, both in structure and function, to the RCC1 gene of mammals and the PIM1 gene of Schizosaccharomyces pombe, both of which appear to regulate entry into mitosis and chromosome condensation. In this report we demonstrate that, after a shift of prp20 mutants to the restrictive temperature, transcripts of several genes (CUP1, CYH2, and GAL10) are produced that extend 1-10 kb beyond their normal polyadenylation sites. The failure in 3'-end formation occurs within 1-2 min of the temperature shift. Transcription initiation also is disrupted, in that initiation sites upstream of the normal cap site are used. mRNA transport from nucleus to cytoplasm also is perturbed: In situ hybridization using an oligo(dT) probe demonstrates accumulation of poly(A) in the nucleus, consistent with the accumulation of longer bulk poly(A) (up to approximately 90-100 nucleotides) and with a failure to transport newly synthesized RNA to the cytoplasm. We demonstrate that prp20 and rna1 mutants are very similar, if not identical, with respect to each of these biochemical phenotypes. In light of the putative role of PRP20 in mitotic control, our results suggest a common step in that process and multiple steps in mRNA synthesis and maturation. We speculate that the perturbations in mRNA processing are the result of effects on the chromatin-nascent RNP-transcription complex or misregulation of a cell cycle component that modifies multiple mRNA-processing activities.

Base Sequence↗
PubMed1989

Oocyte and somatic tyrosine tRNA genes in Xenopus laevis.

Over a period of many months, Xenopus oocytes stockpile large quantities of tRNA for use during the first few hours of embryogenesis. To test the idea that these tRNAs are transcribed from one set of genes and that another set is used by somatic cells, we used synthetic oligonucleotides to analyze the sequence and steady-state levels of unspliced tyrosine tRNA precursors in Xenopus laevis oocytes, embryos, and cultured kidney cells. These analyses identify four kinds of tyrosine tRNA genes, two oocyte-type and two somatic-type, whose unspliced transcripts are distinguishable from one another by their different 5' leader and intervening sequences. The oocyte-type tyrosine tRNA precursors are present in oocytes, very abundant in gastrula embryos, but absent from postembryonic somatic cells. The somatic-type precursors are undetectable in oocytes but are found in gastrula and later stage embryos and in somatic cells. The major switch from oocyte-type to somatic-type transcripts occurs early during embryogenesis, between the midblastula transition and the onset of neurulation, but some oocyte-type precursors are also detectable in tadpoles.

Animals↗
PubMed1988

A third striated muscle actin gene is expressed during early development in the amphibian Xenopus laevis.

During early embryonic development in the frog Xenopus laevis, several muscle-specific actin genes encoding distinct actin protein isoforms are activated in cells of the embryonic muscle. In addition to the cardiac (or alpha 1) and skeletal (or alpha 2) actin genes, a third muscle-specific actin gene is expressed in the same embryonic tissue. We have determined the complete nucleotide sequence of this third gene and examined its expression in embryonic and adult tissues. During embryogenesis, this femoral (alpha 3) actin gene is activated several hours later than its cardiac and skeletal counterparts and its transcripts are first detected after neurulation. The gene encodes a skeletal-type actin protein and is expressed exclusively in skeletal muscle in the adult frog. Two copies of this gene have been isolated from the tetraploid species Xenopus laevis, differing by only a few nucleotides in their protein-coding sequence. The related, diploid species, Xenopus tropicalis, possesses a single copy of the alpha 3 gene and its transcript is similarly conserved in nucleotide sequence. However, the X. tropicalis gene is expressed exclusively in embryonic stages of development. Comparison of the X. laevis and X. tropicalis alpha 3 gene promoters reveals extensive sequence homology, including several copies of a repeated motif that is common to other vertebrate striated-muscle actin gene promoters.

Actins↗
PubMed1988

Different regulatory elements are required for cell-type and stage specific expression of the Xenopus laevis skeletal muscle actin gene upon injection in X.laevis oocytes and embryos.

In the present study, we demonstrate by transcript mapping that the injected Xenopus skeletal muscle alpha-actin gene is transcribed and spliced in Xenopus oocytes but not correctly initiated at the alpha-actin promoter. This leads to correctly spliced transcripts even if constructs without putative promoter sequences are injected. On the other hand, alpha-actin transcripts are translated in injected oocytes as shown by the detection of alpha-actin protein. By contrast, correctly initiated alpha-actin transcripts can be found in neurula embryos when the injected clone contains 5' flanking sequences extending from +27 to -680. alpha-actin gene fragments without the 680 nucleotides 5' flanking region are activated unspecifically after midblastula transition, whereas the clones carrying this region are activated correctly at the end of gastrulation. Cell type specific expression seems to be modulated by sequences within the transcribed region.

Actins↗
PubMed1987

A processed gene coding for a sarcomeric actin in Xenopus laevis and Xenopus tropicalis.

A processed gene potentially coding for a sarcomeric actin has been identified in Xenopus laevis and in the more primitive species X. tropicalis. The peptides encoded in these two species differ by two out of 377 amino acid residues. On the basis of the amino acid substitutions, the encoded peptide was identified as an alpha-skeletal actin in X. laevis and as an alpha-cardiac actin in X. tropicalis. Northern blot analysis and S1 mapping experiments suggest that in X. tropicalis the gene is expressed in embryos and adult heart. In X. laevis, transcripts homologous to this gene were found in embryos and in adult tissues, but predominantly in skeletal muscle rather than in heart.

Actins↗
PubMed1986

Isolation and characterization of sarcomeric actin genes expressed in Xenopus laevis embryos.

A Xenopus laevis complementary DNA (cDNA) library prepared from messenger RNAs extracted from embryos has been screened for actin-coding sequences. Two cDNA clones corresponding to an alpha cardiac and an alpha skeletal muscle actin mRNA have been identified and characterized. From a genomic library, we have furthermore isolated the genes that correspond to the characterized cDNAs. In addition we have identified an actin processed gene which seems to be derived from a second type of skeletal muscle actin gene. Southern blot analysis of X. laevis DNA reveals that each of the three genes is present in at least two copies. In Xenopus tropicalis, a similar Southern blot analysis demonstrates that the three alpha actin genes exist as single copy. This result correlates with the genome duplication that has been proposed to have occurred recently in a X. laevis ancestor. A sequence comparison of the X. laevis cardiac and skeletal muscle actin cDNAs shows that the encoded peptides are highly conserved. Nevertheless, the numerous nucleotide changes at silent mutation sites suggest that the genes originated before the amphibia/reptile-bird divergence, more than 350 million years ago. Comparison of the promoters of the cardiac and skeletal actin genes, which are co-expressed in embryos, reveals a few common structural sequence elements.

Actins↗