Biomedical subjects

M Köster

Publications and source records attributed to M Köster.

48 records · Page 3Linked to original sources

PubMed1991

cDNA sequence of Xenopus laevis bone morphogenetic protein 2 (BMP-2).

Screening of a Xenopus laevis ovary cDNA library with an oligonucleotide derived from the activin A sequence led to the isolation of several clones belonging to the TGF-beta supergene family. One of these clones codes for the Xenopus bone morphogenetic protein 2 (BMP-2). The deduced protein contains 398 amino acids with a predicted Mr of 45,581. Within the C-terminal 114 amino acids constituting the mature, biologically active protein there are only four exchanges (three of them are conservative ones) as compared to the corresponding human sequence.

Amino Acid Sequence↗

PubMed1991

Structure, expression and in vitro functional characterization of a novel RNA binding zinc finger protein from Xenopus.

Large multigene families of zinc finger proteins are expressed in vertebrates. One way of approaching their function is to characterize their structure, expression and biochemical properties. XFG 5-1 is a Xenopus zinc finger protein which is widely transcribed in oocytes, embryos and adult tissues. It carries a novel, non-finger repeat structure, which is common to a subfamily of Xenopus zinc finger proteins. The bacterially expressed protein exhibits specific RNA homopolymer binding activities with the zinc finger domain being sufficient for this ability. These findings suggest that XFG 5-1 serves a general biological function involving its RNA binding capacity.

Amino Acid Sequence↗

PubMed1991

Bone morphogenetic protein 4 (BMP-4), a member of the TGF-beta family, in early embryos of Xenopus laevis: analysis of mesoderm inducing activity.

We have screened a Xenopus ovary cDNA library using a synthetic oligonucleotide derived from that part of the inhibin beta A sequence, which is highly conserved within the TGF-beta family. Out of several clones yielding autoradiographic signals four turned out to represent Xenopus counterparts to the human bone morphogenetic protein 4 (BMP-4). Each two of the four sequences are nearly identical and probably account for different alleles whereas the two pairs showing 5% divergence may have arisen by genome duplication in this tetraploid species. The amino acid sequence of the Xenopus protein is 80% homologous to the human sequence showing no single exchange within the last 100 amino acids at the C-terminus. This region, which constitutes the main part of the mature, biologically active protein, also exhibits substantial homologies to other representatives of the TGF-beta family, especially to the Drosophila DPPC protein. Transfection of COS-1 cells with the Xenopus BMP-4 sequence under control of the CMV-promoter leads to the secretion of a protein which exhibits mesoderm inducing activity when tested with animal cap explants from Xenopus blastula stage embryos.

Amino Acid Sequence↗

PubMed1991

Coxarthrosis and physical work load.

A case-referent study was performed on the possible relationship between physical work loads and an increased risk of developing coxarthrosis. The cases were 239 male recipients of a hip prosthesis as a result of severe idiopathic coxarthrosis; the referents were 302 men randomly selected from the general population. The work load was assessed through an interview and a self-administered questionnaire on the men's specific work periods. Men highly exposed to dynamic or static work loads had an increased relative risk of 2.42 (95% confidence interval 1.45-4.04) for developing coxarthrosis when compared with men with low exposure. Men with high exposure to heavy lifting between the ages of 30 and 49 years had the highest relative risk, 3.31 (95% confidence interval 1.97-5.57). Long-time exposure to physical work loads seems to be a risk factor for severe coxarthrosis among men.

Adult↗

PubMed1990

Sequence analysis of the upstream regions of Xenopus laevis beta-globin genes and arrangement of repetitive elements within the globin gene clusters.

The globin gene clusters of Xenopus laevis are interspersed by various different repetitive DNA elements. A specific repeat, the JH12 element, has been mapped by Southern analysis and some of its locations have been subsequently confirmed by nucleotide sequencing. JH12 family members seem to represent mobile genetic elements and display a high degree of divergence. The nucleotide sequences upstream to the adult beta I-globin gene and to the two coordinately expressed larval beta I- and beta II-globin genes have been determined and compared to those of the adult alpha-genes. Besides some repetitive DNA elements and a short sequence of rather weak homology we have found no characteristic sequence motifs to be common to the adult alpha- and beta-genes. The two larval beta-genes share one short sequence element being absent from the adult genes. This might reflect completely different sequence requirements for protein interactions and for the regulation of adult and larval globin gene expression.

Animals↗

PubMed1990

Two different mRNAs coding for identical elongation factor 1 alpha (EF-1 alpha) polypeptides in Xenopus laevis embryos.

Two related but clearly different cDNA clones corresponding to elongation factor 1 alpha (EF-1 alpha) mRNAs were isolated from a Xenopus laevis gastrula-stage library. Whereas the nucleotide sequences of these two cDNAs differ within the coding region at 49 out of 1386 positions (3.5%), the derived amino acid sequences are completely identical, thereby indicating a substantial evolutionary constraint on this translation factor. Southern-blot analysis of genomic DNA suggests that, besides the two closely related EF-1 alpha genes investigated in this study, other more-distantly related genes may exist in the X. laevis genome. Transcription of EF-1 alpha genes during oogenesis and embryonic development was studied by Northern-blot analysis and by in situ hybridizations. A high amount of EF-1 alpha mRNA was detected in previtellogenic oocytes. At later stages of embryonic development, EF-1 alpha mRNA was found to be accumulated in translationally active tissues.

Animals↗

PubMed1989

Second-order repeats in Xenopus laevis finger proteins.

The primary structure of 342 finger repeats encoded in 42 different cDNA clones isolated from Xenopus laevis oocyte and gastrula cDNA libraries has been determined. Comparative sequence analysis of the predicted protein sequences results in a consensus repeat sequence that has an extended conserved segment of 16 amino acid residues, including the evolutionary conserved H/C link element, connected to a highly variable segment that is located in the finger loop region. Groups of tandem finger repeats are found to be organized in distinct higher-order structural units, with a pair of mutually distinct fingers being the most frequently observed second-order repeat unit. Structural features observed are discussed in respect to existing models for Zn finger structure and function.

Amino Acids↗

PubMed1989

An antisense transcript from the Xenopus laevis bFGF gene coding for an evolutionarily conserved 24 kd protein.

Screening of a Xenopus laevis oocyte cDNA library with a rat basic fibroblast growth factor (bFGF) cDNA led to the isolation of a 1.35 kb sequence containing exon III of the bFGF gene. Reverse complementary listing of this sequence revealed a polyadenylated transcript with an open reading frame coding for an unknown protein of mol. wt 24,292 daltons. The coding part of bFGF exon III is located in this putative mRNA in opposite direction within the 3' untranslated region. By hybridization studies on transcription orientation with single-stranded probes it could be proven that this transcript actually represents an antisense transcript to part of the Xenopus bFGF gene. Sequence organization on corresponding genomic fragments revealed that it is processed from a larger precursor by splicing mechanisms. Sequence comparison with elongated transcripts from the bFGF gene in human hepatoma has shown that the gene coding for the antisense mRNA is evolutionarily conserved.

Amino Acid Sequence↗

PubMed1989

Evolutionary conserved modules associated with zinc fingers in Xenopus laevis.

Many DNA-binding proteins that are involved in the differential regulation of gene expression are composed of multiple discrete modules. Association of the homeobox-encoded helix-turn-helix DNA-binding motif with conserved modules, such as the paired box or the POU domain, has led to the definition of structurally and functionally related subfamilies of regulatory proteins. The zinc finger, which is the second major nucleic acid-binding motif characterized to date, defines large multigene families in higher eukaryotes; we have isolated more than 100 Xenopus finger protein-encoding cDNAs and in this study we show that at least 10 of these clones share extensive sequence homologies in a region of more than 200 amino acids in the N-terminal nonfinger portion of the predicted proteins, which is connected to variable finger clusters. We refer to this element as a finger-associated boxes (FAX) domain. Cross-hybridization with human genomic DNA indicates that the finger-associated boxes domain is evolutionary conserved. Northern blot analysis shows that the corresponding genes are differentially expressed in the course of early Xenopus embryogenesis.

Amino Acid Sequence↗

PubMed1988

Oocyte and somatic 5S ribosomal RNA and 5S RNA encoding genes in Xenopus tropicalis.

We have investigated the structure of oocyte and somatic 5S ribosomal RNA and of 5S RNA encoding genes in Xenopus tropicalis. The sequences of the two 5S RNA families differ in four positions, but only one of these substitutions, a C to U transition in position 79 within the internal control region of the corresponding 5S RNA encoding genes, is a distinguishing characteristic of all Xenopus somatic and oocyte 5S RNAs characterized to date, including those from Xenopus laevis and Xenopus borealis. 5S RNA genes in Xenopus tropicalis are organized in clusters of multiple repeats of a 264 base pair unit; the structural and functional organization of the Xenopus tropicalis oocyte 5S gene is similar to the somatic but distinct from the oocyte 5S DNA in Xenopus laevis and Xenopus borealis. A comparative sequence analysis reveals the presence of a strictly conserved pentamer motif AAAGT in the 5'-flanking region of Xenopus 5S genes which we demonstrate in a separate communication to serve as a binding signal for an upstream stimulatory factor.

Animals↗

PubMed1988

The finger motif defines a multigene family represented in the maternal mRNA of Xenopus laevis oocytes.

We have screened Xenopus laevis cDNA and genomic libraries for finger motif encoding sequences by use of a synthetic oligonucleotide probe coding for a stretch of conserved amino acids, the H/C-link, which joins individual finger loops in several multi-fingered proteins. Our studies reveal that a large number of different cDNA clones encode amino acid sequences predicting multiple units of the metal-coordinating finger structure. Derived proteins are different from each other as well as from the two examples of Xenopus finger proteins reported to date, TFIIIA and X.fin. The 109 finger repeats characterized are derived from 14 different cDNA clones and have been analysed for the presence of conserved and highly variable amino acids, revealing a close structural relatedness among each other as well as with a few selected finger domains from Drosophila and mouse proteins. The results from this comparative sequence analysis are also discussed in terms of the existing models for DNA binding. All sequences are identified in an ovary cDNA library but the patterns of mRNA level for individual finger clones vary greatly during early development. The prevalence of these structures in the oocyte suggests that part of the maternal information for the realization of the developmental program utilized in Xenopus embryogenesis might be transmitted in the form of regulatory, nucleic-acid-binding proteins.

Amino Acid Sequence↗

PubMed1986

Sequence analysis of the larval beta II-globin gene of Xenopus laevis.

The 1822 bp sequence of the larval Xenopus laevis beta II-globin gene is reported together with 240 bp upstream of the gene and 190 bp beyond the site of polyadenylation. The mRNA start point was determined by primer extension as well as nuclease S1 mapping and the polyadenylation site by comparison of the gene sequence to the mRNA sequence derived from a corresponding cDNA clone. Like other vertebrate globin genes, this gene comprises three exons interrupted by two intervening sequences (IVS). IVS I spans over 582 nucleotides and interrupts the exon sequences within codon 30. IVS II is located between the codons 104/105 and spans over 617 nucleotides. The 5' region of the gene contains the canonical TATAA homology at position -31. Comparison of the upstream sequence to that of Xenopus laevis larval beta I-globin gene revealed a conserved sequence, located between nucleotide positions -60 and -87, which might function as regulatory element of transcription. Whereas the upstream region of the larval beta II-globin gene does not contain a CAAT box, we notice a reiterated AAATGA motif and discuss its possible significance.

Amino Acid Sequence↗