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K Damm

Publications and source records attributed to K Damm.

At least 19 recordsLinked to original sources
PubMed1998

One-step affinity purification protocol for human telomerase.

Human telomerase is a ribonucleoprotein (RNP) enzyme, comprising protein components and an RNA template that catalyses telomere elongation through the addition of TTAGGG repeats. Telomerase function has been implicated in aging and cancer cell immortalization. We report a rapid and efficient one-step purification protocol to obtain highly active telomerase from human cells. The purification is based on affinity chromatography of nuclear extracts with antisense oligonucleotides complementary to the template region of the human telomerase RNA component. Bound telomerase is eluted with a displacement oligonucleotide under mild conditions. The resulting affinity-purified telomerase is active in PCR-amplified telomerase assays. The purified telomerase complex has a molecular mass of approximately 550 kDa compared to the approximately 1000 kDa determined for the telomerase RNP in unfractionated nuclear extracts. The purification protocol provides a rapid and efficient tool for functional and structural studies of human telomerase.

Base Sequence↗
PubMed1998

Mouse fibroblast-activation protein--conserved Fap gene organization and biochemical function as a serine protease.

The human fibroblast-activation protein (FAP), a member of the serine protease family, was discovered as an inducible type-II cell-surface glycoprotein selectively expressed by reactive stromal fibroblasts of epithelial cancers and healing wounds. Antibodies directed against human FAP have a clinical use for antibody-based tumor imaging. As part of an effort to generate animal models of FAP expression in epithelial tumorigenesis and wound healing, we previously cloned the cDNA encoding the mouse FAP homolog. In this study, we used PCR/restriction-fragment length polymorphism, identified in interspecific back-crosses between Mus musculus and Mus spretus, to map the Fap gene locus to a region of mouse chromosome 2, known to be syntenic to the previously identified FAP gene locus on human chromosome 2q23. The Fap gene spans approximately 60 kb and contains 26 exons ranging in size from 46 bp to 195 bp. This genomic organization is very similar to that of the human FAP locus. Similar to the gene encoding dipeptidyl peptidase IV (DPP IV), the nucleotides encoding the serine protease consensus motif, WGWSYGG, are split between two exons, a feature distinct from classical serine proteases. Consistent with the similarity to DPP IV, a chimeric FAP fusion protein expressed in a baculovirus system has dipeptidyl peptidase activity.

Animals↗
PubMed1995

Domains of the human androgen receptor and glucocorticoid receptor involved in binding to the nuclear matrix.

Steroid receptors have been reported to bind to the nuclear matrix. The nuclear matrix is operationally defined as the residual nuclear structure that remains after extraction of most of the chromatin and all soluble and loosely bound components. To obtain insight in the molecular mechanism of the interaction of steroid receptors with the nuclear matrix, we studied the binding of several deletion mutants of the human androgen receptor (hAR) and the human glucocorticoid receptor (hGR) to the nuclear matrix. Receptor binding was tested for two different nuclear matrix preparations: complete matrices, in which most matrix proteins are retained during the isolation procedure, and depleted matrices, which consist of only a subset of these proteins. The results show that the C-terminal domain of the hAR binds tightly to both depleted and complete matrices. In addition, at least one other domain of the hAR binds to complete matrices but not to depleted matrices. In contrast to the hAR, the hGR binds only to complete matrices. For this interaction both the DNA-binding domain and the C-terminal domain of the hGR are required, whereas the N-terminal domain is not. We conclude that specific protein domains of the hAR and the hGR are involved in binding to the nuclear matrix. In addition, our results indicate that the hAR and the hGR are attached to the nuclear matrix through different molecular interactions.

Cell Line↗
PubMed1993

Identification of a domain required for oncogenic activity and transcriptional suppression by v-erbA and thyroid-hormone receptor alpha.

v-erbA, a mutated version of the chicken thyroid hormone (TH) receptor type alpha, can inhibit hormonal induction of target genes. In addition, v-erbA acts as a constitutive repressor of the basal promoter activity. In vivo, v-erbA can arrest the differentiation of erythroid precursor cells and suppresses transcription of erythrocyte-specific genes. We show that the v-erbA protein of the transformation-defective avian erythroblastosis virus mutant (AEVtd359) fails to suppress basal transcription level and exhibits impaired ability in antagonizing the TH and retinoic acid response. The inactivating mutation is a 1-nt change leading to a Pro-->Arg replacement in the "hinge region" of v-erbA protein. Introducing this mutation in the context of TH receptor alpha selectively inactivates the suppressor function, while hormone-binding and transcriptional-activation properties are unaffected. These data suggest that trans-repression rather than a dominant negative block of TH-receptor or retinoic acid-receptor activation may represent the primary molecular property underlying erbA oncogenesis.

Alpharetrovirus↗
PubMed1993

Pharmacological and functional characterization of human mineralocorticoid and glucocorticoid receptor ligands.

We characterized the pharmacological profiles of the human mineralocorticoid and glucocorticoid receptor for 11 natural and synthetic steroids regarding binding pharmacology, intracellular localization of hormone-receptor complexes, and agonistic or antagonistic properties at the gene expression level. The sex steroid progesterone bound with an affinity (ki < 0.01 nM) even higher than that of aldosterone to the human mineralocorticoid receptor and effectively antagonized the effect of aldosterone via the human mineralocorticoid receptor in functional co-transfection assays. This indicates that progesterone has potent antimineralocorticoid properties, while its antiglucocorticoid effects were less pronounced. The partial agonistic activities of antihormones in this assay suggest a direct interaction of antihormone-receptor complexes with the response elements on the DNA. These results are supported by immunofluorescence studies, in which both unliganded human mineralocorticoid and glucocorticoid receptors were distributed throughout the cytoplasm and nucleus, whereas agonist- as well as antagonist-receptor complexes showed an exclusively nuclear localization. These results contribute to the understanding of antihormone pharmacology and increase our understanding of the role of human mineralocorticoid and glucocorticoid receptors in physiological processes during different endocrine states.

Aldosterone↗
PubMed1993

Functional inhibition of retinoic acid response by dominant negative retinoic acid receptor mutants.

The diverse effects of retinoids on the development, growth, and homeostasis of vertebrate organisms are mediated in part by three distinct isoforms of retinoic acid receptors (RARs). These proteins, which are structurally and functionally closely related to thyroid hormone receptors and the oncogene product v-ErbA, regulate patterns of gene expression in target tissues. One approach to study the distinct effects of retinoic acid in cells is to subvert this activity of endogenous receptors by expression of dominant negative receptor derivatives. We demonstrate here that RAR alpha, RAR beta, and RAR gamma can be converted into potent negative transcriptional regulators that block wild-type RAR function. Furthermore, these mutant RARs, but not the wild-type receptors, actively repress the basal transcription level of target promoters. When expressed in transgenic mice, the most potent of these inhibitory receptor mutants is apparently able to disturb developmental processes by inducing a cleft palate in transgenic offspring.

Amino Acid Sequence↗
PubMed1993

Progesterone receptor-mediated effects of neuroactive steroids.

Several 3 alpha-hydroxysteroids accumulate in the brain after local synthesis or after metabolization of steroids that are provided by the adrenals. The 3 alpha-hydroxy ring A-reduced pregnane steroids allopregnanolone and tetrahydrodeoxycorticosterone are believed not to interact with intracellular receptors, but enhance GABA-mediated chloride currents. The present study shows that these neuroactive steroids can regulate gene expression via the progesterone receptor. The induction of DNA binding and transcriptional activation of the progesterone receptor requires intracellular oxidation of the neuroactive steroids into progesterone receptor active 5 alpha-pregnane steroids. Thus, at physiological concentrations, these neuroactive steroids regulate neuronal function through their effects on both transmitter-gated ion channels and steroid receptor-regulated gene expression.

Base Sequence↗
PubMed1993

ErbA: tumor suppressor turned oncogene?

Cancer has been commonly linked to aberrant proliferation and a failure of the transformed cells to differentiate. Activated proto-oncogenes are thought to provide continuous proliferation signals that enhance the growth of these cells. Conversely, cellular transformation may also be achieved by the inactivation of genes whose normal function is to constrain cell growth by either suppressing proliferation or inducing differentiation. Such an inactivation could result from dominant-negative mutations, leading to the expression of abnormal proteins that inhibit the function of their normal counterparts. A prototype example is the v-erbA oncogene of the avian erythroblastosis virus (AEV), which antagonizes the transcriptional regulatory function of the chicken c-ErbA/thyroid hormone receptors (c-ErbA/TR) and the structurally related retinoic acid receptors (RARs). The result of this inhibition is a loss of hormone responsiveness and hormone-induced differentiation. Here we have a parallel to the tumor suppressor gene where it is also a loss of function that induces the transformation process. In this way, the normal, hormone-activated c-ErbA/TRs and RARs act as growth suppressors because the resulting differentiated cells irreversibly lose proliferative potential. In this article, the properties of v-ErbA will be discussed in the context of c-ErbA/thyroid hormone and retinoic acid receptor function.

Amino Acid Sequence↗
PubMed1993

A functional promoter directing expression of a novel type of rat mineralocorticoid receptor mRNA in brain.

The authors have identified two types of hippocampal cDNAs for the rat mineralocorticoid receptor (rMR) which are identical in the protein coding domain but differ in their 5'-untranslated sequences. One of these clones encodes a novel type of rMR cDNA with a high homology to a previously described human MR cDNA isolated from the kidney. A genomic clone containing the 5'-end of the rat MR gene was isolated. The 12.7 kb genomic region contains the 5'-coding exon with the translational start site and contiguous DNA sequences encoding the N-terminal domain of the rMR. A 240 bp region homologous to the 5'-untranslated sequences of the novel rMR cDNA was located 5.2 kb upstream the protein coding region. Characterization of the nucleotide sequence preceding this exon revealed several features characteristic for promoters of so-called 'housekeeping genes'. The sequence analyzed is 635 bp in length, is rich in G+C nucleotides (63%) and lacks TATA or CAAT regulatory elements. It contains three putative binding sites for transcription factor Sp1 as well as several short sequences that are similar to known cis-acting enhancers or binding sites for transcription factors. In transient transfection experiments employing the luciferase reporter gene and the CV1 cell line this region exhibits substantial promoter activity. These experiments demonstrate that expression of the rat MR gene in the hippocampus results in at least two transcripts with different 5'-untranslated exons.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Transactivation and synergistic properties of the mineralocorticoid receptor: relationship to the glucocorticoid receptor.

The human mineralocorticoid (hMR) and glucocorticoid (hGR) receptors mediate biological responses to adrenal corticosteroids and synthetic ligands. In transient transfection studies, corticosteroid-responsive promoters were used to monitor the hormone-dependent transcriptional regulatory properties of both receptors. The hMR mediates a lower stimulation of the transcription rate than the hGR and does not show cooperative activity on promoters containing multiple palindromic glucocorticoid-responsive elements. The functional importance of the amino-terminus in this differential response was demonstrated by hMR/hGR hybrid receptors in which this region was exchanged or deleted. These experiments revealed that the hMR amino-terminus does not provide the strong transactivation function present in the equivalent hGR domain and, in contrast to the hGR amino-terminus, interferes with the synergistic activity mediated by the DNA- and ligand-binding domains of both receptors.

Base Sequence↗
PubMed1992

A mutated retinoic acid receptor-alpha exhibiting dominant-negative activity alters the lineage development of a multipotent hematopoietic cell line.

The retinoic acid receptor (RAR alpha) is expressed in virtually all hematopoietic lineages, but the role of this transcription factor in regulating the growth and differentiation of hematopoietic progenitors is unknown. We have constructed a mutant RAR alpha that both exhibits dominant-negative activity against the normal RAR alpha in transient expression assays in mouse fibroblasts and inhibits retinoic acid-induced neutrophilic differentiation of the HL-60 human promyelocytic leukemia cell line. When this dominant-negative RAR alpha construct is introduced into the multipotent interleukin-3-dependent FDCP mix A4 murine hematopoietic cell line, there is a rapid switch from spontaneous neutrophil/monocyte differentiation to basophil/mast cell development. Thus, in this multipotent hemopoietic cell line the normal RAR alpha transcription factor and/or related molecules appear to promote the differentiation of neutrophils and monocytes but suppress the development of basophils/mast cells.

3T3 Cells↗
PubMed1991

[Distribution of mononuclear cells in peripheral blood of females with spontaneous abortion].

The quantitative distribution of peripheral T cells, monocytes/granulocytes, natural killer cells and B cells was estimated in aborting women using the peroxidase-antiperoxidase technique with monoclonal antibodies. 30 women with spontaneous abortions were included in the study and 30 fertile and 50 healthy pregnant women as control groups. It could established that the normal pregnancy has no influence on the distribution of mononuclear cells. In cases with threatened abortions was the number of monocytes/granulocytes and of natural killer cells increased if the loss of pregnancy occurred. The differentiation of mononuclear cells may be helpful for the prognosis of abortions.

Abortion, Habitual↗
PubMed1990

The v-erb A oncogene causes repression of erythrocyte-specific genes and an immature, aberrant differentiation phenotype in normal erythroid progenitors.

We have compared the effects of the v-erb A oncogene on proliferation and differentiation of normal erythroid progenitors with those of tyrosine kinase oncogenes, e.g. v-sea. For this, a v-erb A retrovirus containing the neomycin resistance gene as a selectable marker or, alternatively, a v-erb A-ts v-sea retrovirus were used to infect normal bone marrow cells. V-erb A induced the outgrowth of immature, erythropoietin(EPO)-dependent erythroid cells from infected bone marrow which ceased to proliferate and disintegrated after 9 to 18 divisions. In contrast, ts-v-sea erythroblasts grew for the expected 25 to 40 population doublings in the absence of EPO. Transcription of the erythrocyte genes carbonic anhydrase II and erythrocyte anion transporter was significantly inhibited in v-erb A infected erythroblasts, indicating that v-erb A alone was sufficient for the repression of the erythrocyte-specific genes observed in AEV-transformed leukemic cells. A detailed analysis of the differentiation phenotype induced by v-erb A in erythroblasts (in the presence or absence of a temperature-inactivated ts sea oncogene) indicates that v-erb A-erythroblasts express a partially mature, aberrant phenotype characterized by the coexpression of mature and immature differentiation antigens. This phenotype clearly differs from that induced by tyrosine kinase oncogenes in erythroid cells.

Animals↗
PubMed1989

Protein encoded by v-erbA functions as a thyroid-hormone receptor antagonist.

The thyroid-hormone receptor can, in the absence of its ligand, suppress activity of a responsive promoter. Addition of thyroid hormone, however, results in the stimulation of expression. The oncogenic derivative of the thyroid-hormone receptor, v-erbA, acts as a constitutive repressor and, when coexpressed with the receptor, blocks activation by thyroid hormone. Thus, v-erbA may be the first example of a dominant negative oncogene.

Animals↗
PubMed1989

Molecular cloning of the chicken myelomonocytic growth factor (cMGF) reveals relationship to interleukin 6 and granulocyte colony stimulating factor.

Normal as well as retrovirally transformed avian myeloid precursor cells require the colony stimulating factor cMGF for their survival, proliferation and colony formation in vitro. cMGF has been shown to be a glycoprotein which is active in the picomolar concentration range. Co-expression of kinase type oncogenes in v-myb or v-myc transformed myeloid cells induces cMGF expression and confers factor independence via an autocrine mechanism. Here we describe the molecular cloning of cMGF from a myeloblast cDNA library and show that it is a 201 amino acid residue secretory protein which is modified by signal peptide cleavage and glycosylation during translocation into the lumen of membrane vesicles. A bacterially expressed trpE-cMGF fusion protein induces proliferation of E26 transformed myeloblasts in a cMGF bioassay suggesting that glycosylation is not absolutely necessary for biological activity. Sequence comparison reveals that cMGF is distantly related to G-CSF and IL-6.

Amino Acid Sequence↗
PubMed1987

A single point mutation in erbA restores the erythroid transforming potential of a mutant avian erythroblastosis virus (AEV) defective in both erbA and erbB oncogenes.

We have characterized the v-erbA and v-erbB oncogenes of td359, a transformation-defective mutant of avian erythroblastosis virus (AEV) unable to transform erythroblasts, and the revertant r12, obtained after in vivo passage of the mutant. Molecular cloning, sequencing, construction of chimeric viruses and testing of their oncogenic capacities revealed that both oncogenes of td359 are mutated and biologically defective. The r12 virus, although still containing a mutant v-erbB gene, recovered its erythroid transforming potential by acquiring a highly active gag-erbA gene. These results demonstrate that two co-operating oncogenes, an active v-erbA and a defective v-erbB, can transform a cell type not transformed by either oncogene alone. Furthermore, a single amino acid substitution inactivated the td359 v-erbA protein and we show that its reversion led to the reactivation of the protein. This lesion is located in the same region as several previously described inactivating mutations of glucocorticoid receptors, suggesting that the structure/function relationship of the virally transduced form of the c-erbA/thyroid hormone receptor is closely similar to that of steroid hormone receptors.

Alpharetrovirus↗