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J Stalder

Publications and source records attributed to J Stalder.

31 records · Page 2Linked to original sources
PubMed1984

The primary structure of the larval beta 1-globin gene of Xenopus laevis and its flanking regions.

We present the complete nucleotide sequence of the larval beta I-globin gene of Xenopus laevis including 240 nucleotides of the 5' flanking region and 594 nucleotides beyond the polyadenylation site. The site of transcription initiation was mapped by S1 nuclease, and the site of polyadenylation was determined by comparison with corresponding cDNA clones. The larval Xenopus beta I-gene shows the same internal structure as the beta-globin genes of higher vertebrates, viz. 3 exons interrupted by 2 intervening sequences. The first intervening sequence, which is of exceptional length, spans over 564 nucleotides and interrupts the coding sequence at amino acid 30, whereas the second one comprises 968 nucleotides and is located between the amino acids 104 and 105. The second intervening sequence contains a long inverted repeat of almost perfect homology. The 5' flanking region contains a TATA- and a CAAT-box at positions -33 and -58, respectively. An additional TATA-box is located at -197 and two more CAAT-boxes occur at positions -105 and -237.

Amino Acid Sequence↗
PubMed1983

Defective viral RNAs in Aedes albopictus C6/36 cells persistently infected with Semliki Forest virus.

A persistent infection of Semliki Forest virus (SFV) has been established in Aedes albopictus C6/36 cells. Only a small number of cells survived the initial infection with this RNA virus and gave rise to a persistently infected culture which produced continuously small amounts of infectious virus. To investigate whether defective viral RNA was analyzed early and late after infection by blot hybridizations. Several defective viral RNAs were detected with a common sequence corresponding to the 3' end of the viral genome during and after the establishment of the persistent infection. These defective viral RNAs resemble the defective interfering RNAs in vertebrate cells generated during serial undiluted passages of standard SFV. The defective viral RNAs are rarely released from cells as virions. The rapid generation of defective viral RNAs may be important for the establishment of a persistent infection in mosquito cells.

Aedes↗
PubMed1983

Extraskeletal myxoid chondrosarcoma. A case report with histochemical and ultrastructural features.

The case of an extraskeletal myxoid chondrosarcoma in a 65-year-old male, localized in the lower right thigh, is presented. The histological, histochemical, and ultrastructural features of this rare tumour are described and compared with those of the pertinent literature. The value of histochemical methods as an aid in differentiating this tumour from other malignant myxoid tumours of soft tissue is emphasized.

Aged↗
PubMed1979

Accessibility of the ribosomal genes to micrococcal nuclease in Physarum polycephalum.

In Physarum polycephalum most genes coding for ribosomal RNA are not integrated in chromosomes, but are located in many copies in the nucleolus as plasmid-like palindromic DNA molecules. To find out whether coding sequences of rDNA are organized in a chromatin-like structure similar to that of bulk chromatin, nuclei were treated with micrococcal nuclease and DNA fragments were isolated. From bulk chromatin multimers of a basic unit of 170-180 base pairs were obtained. Nuclease fragmented DNA hybridized with labelled 19-S + 26-S rRNA was found to give the same saturation value as did unfragmented control DNA. No preferential degradation of ribosomal genes to acid soluble products was observed. A more detailed analysis of the nuclease degradation products was carried out with fragments separated by preparative gel electrophoresis. DNA eluted from the gels was hybridized in solution with labelled 19-S + 26-S rRNA. The coding sequences of rRNA were found to be degraded to approximately nucleosome size slightly more quickly than was the DNA of bulk chromatin. However, the distribution of the rDNA fragments on the gels did not coincide with the distribution of the fragments derived from bulk chromatin nucleosomes and their oligomers. The amount of rDNA in the interband regions was about intermediate between that found in the two adjacent bands. These results lead to the conclusion that the ribosomal genes, most of which are presumably active during rapid growth, are protected by proteins, probably histones. However, the ribosomal genes are present in a structure differing in some way from that of bulk chromatin.

DNA↗
PubMed1979

Isolation of a minichromosome containing the ribosomal genes from Physarum polycephalum.

The ribosomal genes of Physarum polycephalum are located on linear DNA molecules (rDNA) of 38 x 10(6) daltons present in each nucleolus in 100--200 copies. The rDNA is not part of the large chromosomal DNA. These molecules have now been solubilized in the form of transcriptionally active deoxyribonucleoprotein complexes from nucleoli purified through Percoll gradients. The ribosomal chromatin (rDNP) sediments in sucrose gradients as a homogeneous fraction with an approximate sedimentation coefficient of 100 S. It contains alpha-amanitin-resistant RNA polymerase I activity and rDNA as its major (or sole) DNA component. Buoyant density analysis indicates that ribosomal chromatin contains, besides RNA polymerase I, significant amounts of additional protein. RNA synthesized in vitro by the endogenous RNA polymerase is complementary to rDNA and is transcribed mainly from the sequences coding for 19S and 26S ribosomal RNA.

Amanitins↗
PubMed1978

Characterization of chick liver chromatin and analysis of its in vitro transcription products.

Carefully controlled preparation of chromatin from purified chick liver nuclei yielded over 50% native chromatin as shown by the analysis of the nucleosome pattern after micrococcal nuclease digestion. The size of DNA in this chromatin as analyzed on alkaline sucrose gradients varied from 10S to 19S, the majority being 14S. All endogenous RNA polymerases were represented in the chromatin preparation although to different extents: RNA polymerase I was the most and RNA polymerase II the least abundant. Initiation studies showed that endogenous RNA polymerase II was capable of initiating RNA chains during 5 min. Saturation of chromatin with purified homologous RNA polymerase II increased initiation to 10 min. The addition of heparin caused the RNA transcribed to be larger in size and of increased yield. Chromatin transcription with added purified RNA polymerase II in the presence of heparin produced RNA as large as 32S. A chromatin preparation of this kind would therefore be suitable to transcribe any eukaryotic gene invitro provided additional homologous RNA polymerase II is used.Images

Animals↗
PubMed1978

Degradation of the ribosomal genes by DNAse I in Physarum polycephalum.

Treatment of nuclei from Physarum polycephalum with DNAse I leads to DNA fragments with a regular pattern of multiples of 10 nucleotides, when analyzed on gels under denaturing conditions as has been shown for other eukaryotes. Reports from Weintraub and Axel lead to the conclusion, that active genes are preferentially digested by DNAse I. When Physarum chromatin is degraded by DNAse I, the ribosomal genes are no longer available for hybridization with 19-S and 26-S rRNA and are thus preferentially destroyed. Degradation of chromatin from nuclei in mitosis, where no rRNA is synthesized and from nuclei in late G2 phase, where rRNA synthesis is maximal, leads to the same proportion of the ribosomal sequences being lost for hybridization. Therefore the preferential degradation of the ribosomal genes in Physarum by DNAse I probably does not reflect the actual momentary activity of these genes. This suggests that DNAse I treatment may distinguish between active chromatin and very strongly repressed chromatin.

Cell Nucleus↗
PubMedDate not supplied

Primary structure and evolutionary relationship between the adult alpha-globin genes and their 5'-flanking regions of Xenopus laevis and Xenopus tropicalis.

To investigate the evolution of globin genes in the genus Xenopus, we have determined the primary structure of the related adult alpha I- and alpha II-globin genes of X. laevis and of the adult alpha-globin gene of X. tropicalis, including their 5'-flanking regions. All three genes are comprised of three exons and two introns at homologous positions. The exons are highly conserved and code for 141 amino acids. By contrast, the corresponding introns vary in length and show considerable divergence. Comparison of 900 bp of the 5'-flanking region revealed that the X. tropicalis gene contains a conserved proximal 310-bp promoter sequence, comprised of the canonical TATA and CCAAT motifs at homologous positions, and five conserved elements in the same order and at similar positions as previously shown for the corresponding genes of X. laevis. We therefore conclude that these conserved upstream elements may represent regulatory sequences for cell-specific regulation of the adult Xenopus globin genes.

Animals↗