Biomedical subjects

W Schuster

Publications and source records attributed to W Schuster.

At least 19 recordsLinked to original sources

PubMed1992

The mitochondrial gene encoding ribosomal protein S12 has been translocated to the nuclear genome in Oenothera.

The Oenothera mitochondrial genome contains only a gene fragment for ribosomal protein S12 (rps12), while other plants encode a functional gene in the mitochondrion. The complete Oenothera rps12 gene is located in the nucleus. The transit sequence necessary to target this protein to the mitochondrion is encoded by a 5'-extension of the open reading frame. Comparison of the amino acid sequence encoded by the nuclear gene with the polypeptides encoded by edited mitochondrial cDNA and genomic sequences of other plants suggests that gene transfer between mitochondrion and nucleus started from edited mitochondrial RNA molecules. Mechanisms and requirements of gene transfer and activation are discussed.

Amino Acid Sequence↗

PubMed1992

Regenerating good sense: RNA editing and trans splicing in plant mitochondria.

The protein products of plant mitochondrial genes cannot be predicted accurately from genomic sequences, since RNA editing modifies almost all mRNA sequences post-transcriptionally. Furthermore, RNA editing alters leader, trailer and intron sequences, and may be required for processing of these sequences. For several plant mitochondrial transcripts, processing includes trans splicing, which connects exons scattered throughout the genome. The mature transcripts are assembled via split group II intron sequences.

Introns↗

PubMed1992

[Radiation sparing assessment of a child].

In a seven-year old girl who had swallowed a big coin, the position of the foreign body in the stomach was demonstrated sonographically by means of the technique of the fluid filled stomach. Endoscopic removal after 48 hours was arranged without x-ray examination.

Child↗

PubMed1992

[Sonography of pancreatic cancer].

The aim of this retrospective study was to test the quality of pancreatic sonography in a hospital without CT. Out of 25 patients 21 were assessable. We made the correct diagnosis in 76.2% (n = 16) of the cases. The tumour size was between 25 and 60 mm. 20 tumours showed a relatively hypoechoic mass. A dilatation of biliary ducts could be seen in 87.5%. Metastasis of lymph nodes we could only detect in 38.5%, liver metastases in 64.5%. The sensitivity increases with the experience of the examiner, but lot of time is necessary. It is difficult to make a differential diagnosis between carcinoma and pancreatitis. In this cases, CT shows better results. In spite of improvements in sonography, early cancer still is a diagnostic problem.

Adenocarcinoma↗

PubMed1991

RNA editing makes mistakes in plant mitochondria: editing loses sense in transcripts of a rps19 pseudogene and in creating stop codons in coxI and rps3 mRNAs of Oenothera.

An intact gene for the ribosomal protein S19 (rps19) is absent from Oenothera mitochondria. The conserved rps19 reading frame found in the mitochondrial genome is interrupted by a termination codon. This rps19 pseudogene is cotranscribed with the downstream rps3 gene and is edited on both sides of the translational stop. Editing, however, changes the amino acid sequence at positions that were well conserved before editing. Other strange editings create translational stops in open reading frames coding for functional proteins. In coxI and rps3 mRNAs CGA codons are edited to UGA stop codons only five and three codons, respectively, downstream to the initiation codon. These aberrant editings in essential open reading frames and in the rps19 pseudogene appear to have been shifted to these positions from other editing sites. These observations suggest a requirement for a continuous evolutionary constraint on the editing specificities in plant mitochondria.

Amino Acid Sequence↗

PubMed1991

RNA editing in ATPase subunit 6 mRNAs in Oenothera mitochondria. A new termination codon shortens the reading frame by 35 amino acids.

The open reading frame encoding ATPase subunit 6 in Oenothera mitochondria is edited at 21 positions in all cDNA clones investigated. Only one of these events is silent, all others improve similarity between the homologous polypeptides of other species. The introduction of a new UAA termination codon shortens the polypeptide by 35 amino acids to a carboxy terminus conserved in other species. In one of the cDNA clones, an additional editing event was observed resulting in a premature UAA termination codon in the amino terminal region.

Adenosine Triphosphatases↗

PubMed1991

Trans splicing in Oenothera mitochondria: nad1 mRNAs are edited in exon and trans-splicing group II intron sequences.

The complete NADH dehydrogenase subunit 1 (nad1) ORF in Oenothera mitochondria is encoded by five exons. These exons are located in three distant locations of the mitochondrial genome. One genomic region encodes exon a, the second encodes exons b and c, and the third specifies exons d and e. Cis-splicing group II introns separate exons b and c and d and e, while trans-splicing reactions are required to link exons a and b and c and d. The two parts of the group II intron sequences involved in these trans-splicing events can be aligned in domain IV. Exon sequences and the maturase-related ORF in intron d/e are edited by numerous C to U alterations in the mRNA. Two RNA editing events in the trans-splicing intron a/b improve conservation of the secondary structure in the stem of domain VI. RNA editing in intron sequences may thus be required for the trans-splicing reaction.

Amino Acid Sequence↗

PubMed1991

Trans splicing integrates an exon of 22 nucleotides into the nad5 mRNA in higher plant mitochondria.

The genes coding for NADH dehydrogenase subunit 5 (nad5) in mitochondria of the higher plants Oenothera and Arabidopsis are split into five exons that are located in three distant genomic regions. These encode exons a + b, c and d + e, respectively. Maturation of the mRNAs requires two trans splicing events to integrate exon c of only 22 nucleotides. Both trans splicing reactions involve mitochondrial group II intron sequences that allow base pairings in the interrupted domain IV, demonstrating the flexibility of intron structures. The observation of fragmented intron sequences in plant mitochondria suggests that trans splicing is more widespread than previously assumed. RNA editing by C to U alterations in both Oenothera and Arabidopsis open reading frames improves the evolutionary conservation of the encoded polypeptides. Three C to U RNA editing events were observed in intron sequences.

Amino Acid Sequence↗

PubMed1991

Distribution of RNA editing sites in Oenothera mitochondrial mRNAs and rRNAs.

To investigate whether RNA editing in plant mitochondria modifies structural RNAs as well as protein-coding RNAs we compared the genomic-encoded information with the respective transcripts of several genes in Oenothera. The genes analysed are the 5S, 18S and 26 S rRNAs, the alpha-subunit of ATPase (atpA), cytochrome b (cytb), orfB, which is located upstream of cytochrome oxidase subunit III, and the respective leader, trailer and spacer sequences. All open reading frames were found to be edited to some degree. The atpA coding region has the least edited mRNA in Oenothera mitochondria, with only four nucleotides altered in the 1533 nucleotide open reading frame. From this analysis we conclude that frequent RNA editing is indicative of functional protein coding regions in plant mitochondria. The extensive editing in orfB, for example, suggests that this orf codes for a mitochondrial protein. No RNA editing event was found in the 5S rRNA or in the 1824 nucleotides analysed of the 18S rRNA, but two nucleotides were found to be altered in the 1970 nucleotides compared for the 26S rRNA. One nucleotide alteration has changed C to U, the other in reverse U to C. However, only one of five cDNA clones covering this region shows the modifications, similar to many silent editing events in open reading frames. RNA editing in the structural RNAs thus does not seem to be essential for their function in the mitochondrial ribosome.

Adenosine Triphosphatases↗

PubMed1991

Cryptosporidium sp. in stool specimens from diarrhoeic and asymptomatic individuals in the Magdeburg area (East Germany).

Unselected stool specimens from a total of 2,944 individuals with diarrhoea including 1,172 children under 14 years of age were investigated for Cryptosporidium oocysts in the Magdeburg area from 1987 to 1988, 43 (1.46%) were found positive. Three of these were additionally infected with bacterial pathogens (Campylobacter species). In all cases the symptoms of diarrhoea ceased spontaneously after an average of 8 days. The incidence was highest among children and infants under 6 years of age (2.50%). No cryptosporidia were found in stool specimens of 570 healthy individuals of all age groups. Cysts of Giardia sp. were detected more frequently in healthy than in diarrhoeic individuals (3.3% and 2.0%, respectively). The postulation to search for cryptosporidia in all cases of diarrhoea lasting longer than two days is inferred from these results.

Adolescent↗

PubMed1990

RNA editing of ATPase subunit 9 transcripts in Oenothera mitochondria.

The mRNA for subunit 9 of the ATPase (atp9) in the higher plant Oenothera is edited in four nucleotide positions. Three events alter genomic serine and proline codons to triplets specifying leucine. A UGA termination codon is introduced into the reading frame by modification of a CGA arginine codon. This modification shortens the polypeptide by four amino acids. Direct sequencing of PCR amplified cDNA from the total mitochondrial mRNA population gives no indication of partially edited transcripts suggesting a rapid and efficient modification of atp9 transcripts in Oenothera mitochondria.

Amino Acid Sequence↗

PubMed1990

In vitro processing of mitochondrial and plastid derived tRNA precursors in a plant mitochondrial extract.

A lysate of purified mitochondria of the higher plant Oenothera processes in vitro synthesized tRNA precursors to the mature tRNA size. In vitro synthesized transcripts containing genuine plant mitochondrial tRNAs and analogous RNAs from mitochondrial loci with plastid derived tRNA sequences are accurately processed by an RNAase P-like activity to yield the mature 5'-terminus. A four nucleotide deletion in the anticodon stem-loop structure, however, prevents processing. The results show that in vitro transcripts containing tRNAs from sequence fragments of plastid origin integrated in plant mitochondrial genomes can be processed correctly in plant mitochondria, if tRNA sequences and structures are intact.

Base Sequence↗

PubMed1990

Ribosomal protein S14 transcripts are edited in Oenothera mitochondria.

The gene encoding ribosomal protein S14 (rps14) in Oenothera mitochondria is located upstream of the cytochrome b gene (cob). Sequence analysis of independently derived cDNA clones covering the entire rps14 coding region shows two nucleotides edited from the genomic DNA to the mRNA derived sequences by C to U modifications. A third editing event occurs four nucleotides upstream of the AUG initiation codon and improves a potential ribosome binding site. A CGG codon specifying arginine in a position conserved in evolution between chloroplasts and E. coli as a UGG tryptophan codon is not edited in any of the cDNAs analysed. An inverted repeat 3' of an unidentified open reading frame is located upstream of the rps14 gene. The inverted repeat sequence is highly conserved at analogous regions in other Oenothera mitochondrial loci.

Amino Acid Sequence↗

PubMed1990

Transcripts of the NADH-dehydrogenase subunit 3 gene are differentially edited in Oenothera mitochondria.

A number of cytosines are altered to be recognized as uridines in transcripts of the nad3 locus in mitochondria of the higher plant Oenothera. Such nucleotide modifications can be found at 16 different sites within the nad3 coding region. Most of these alterations in the mRNA sequence change codon identities to specify amino acids better conserved in evolution. Individual cDNA clones differ in their degree of editing at five nucleotide positions, three of which are silent, while two lead to codon alterations specifying different amino acids. None of the cDNA clones analysed is maximally edited at all possible sites, suggesting slow processing or lowered stringency of editing at these nucleotides. Differentially edited transcripts could be editing intermediates or could code for differing polypeptides. Two edited nucleotides in an open reading frame located upstream of nad3 change two amino acids in the deduced polypeptide. Part of the well-conserved ribosomal protein gene rps12 also encoded downstream of nad3 in other plants, is lost in Oenothera mitochondria by recombination events. The functional rps12 protein must be imported from the cytoplasm since the deleted sequences of this gene are not found in the Oenothera mitochondrial genome. The pseudogene sequence is not edited at any nucleotide position.

Amino Acid Sequence↗

PubMed1990

Species-specific RNA editing patterns in the mitochondrial rps13 transcripts of Oenothera and Daucus.

Transcripts from the rps13 locus, which encodes ribosomal protein S13, in Oenothera and Daucus mitochondria are edited by several cytidine to uridine transitions in both plants. Analysis of individual cDNA clones and polymerase chain reaction (PCR)-amplified cDNA from the total mitochondrial mRNA population shows different editing patterns in the two species. Although the same genomic triplet is conserved, nucleotides altered in the mRNA of one species are not necessarily edited in the other. Individual editing sites appear to be modified to varying degrees in the mRNA populations in both plant species, indicating that completely edited transcripts constitute only a minor fraction of the rps13 mRNA molecules.

Amino Acid Sequence↗

PubMed1990

Genes for tRNA(Gly), tRNA(His), tRNA(Lys), tRNA(Phe), tRNA(Ser) and tRNA(Tyr) are encoded in Oenothera mitochondrial DNA.

The genes coding for tRNA(Gly), tRNA(His), tRNA(Lys), tRNA(Phe), tRNA(Ser) and tRNA(Tyr) have been identified in Oenothera mitochondrial DNA. Sequence analysis of these genes and their surrounding sequences are presented and compared with other known tRNA genes from plant mitochondria. All six deduced tRNA sequences can be folded into the classical cloverleaf structure model. Only the tRNA(His) gene shows high homology with the corresponding chloroplast gene and thus appears to be derived from a transfer event of chloroplast sequences into the mitochondrial genome. The sequences surrounding this gene, however, show little similarity with the chloroplast genome. The other five deduced tRNAs display a much lower similarity with their chloroplast counterparts and thus appear to be genuine mitochondrial tRNAs. These tRNAs are highly conserved between monocots and dicots with maximally three nucleotides differing between the Oenothera sequences and their wheat homologues. A purine-rich sequence is found upstream of each tRNA gene in Oenothera, similar to wheat mitochondrial tRNA genes, that could be involved in transcription signalling.

Base Sequence↗

PubMed1990

RNA editing in the cytochrome b locus of the higher plant Oenothera berteriana includes a U-to-C transition.

RNA editing in the cytochrome b locus of Oenothera berteriana mitochondria modified a number of cytidine nucleotides to uridines, mostly altering codon identities. One nucleotide alteration involved a reverse modification changing a genomic thymidine to a cytidine in the cDNA sequence. The enzymatic editing activity in higher-plant mitochondria thus appears to be able to catalyze the interconversion of pyrimidines in both directions at specific nucleotides in the mRNA template.

Amino Acid Sequence↗

PubMed1989

RNA editing in plant mitochondria.

Comparative sequence analysis of genomic and complementary DNA clones from several mitochondrial genes in the higher plant Oenothera revealed nucleotide sequence divergences between the genomic and the messenger RNA-derived sequences. These sequence alterations could be most easily explained by specific post-transcriptional nucleotide modifications. Most of the nucleotide exchanges in coding regions lead to altered codons in the mRNA that specify amino acids better conserved in evolution than those encoded by the genomic DNA. Several instances show that the genomic arginine codon CGG is edited in the mRNA to the tryptophan codon TGG in amino acid positions that are highly conserved as tryptophan in the homologous proteins of other species. This editing suggests that the standard genetic code is used in plant mitochondria and resolves the frequent coincidence of CGG codons and tryptophan in different plant species. The apparently frequent and non-species-specific equivalency of CGG and TGG codons in particular suggests that RNA editing is a common feature of all higher plant mitochondria.

Amino Acid Sequence↗