Biomedical subjects

G Posseckert

Publications and source records attributed to G Posseckert.

7 recordsLinked to original sources

PubMed1998

Structural analysis of the amplified IFN-beta and DHFR genes in a Chinese hamster ovary cell line using multicolour FISH analysis.

Multicolour FISH was used to get insight into the structural arrangement of a homogeneously staining region which bears the co-transfected and subsequently co-amplified IFN-beta and DHFR genes in a CHO cell line. On metaphase chromosomes an arrangement of multiple bands with regular spacing is revealed. On extended chromatin fibres a cluster of directly repeated and interspersed IFN-beta and DHFR genes is visible. Up to three clusters were found arranged in tandem. The different chromosomal mechanisms leading to gene amplification are discussed.

Animals↗

PubMed1996

Circulating interleukin-2 receptors are a group of multimeric proteins with immunoreactivity for interleukin-2 receptor alpha, beta, and gamma chains.

Soluble interleukin-2 receptor (sIL-2R) alpha chain serum levels as determined by enzyme-linked immunosorbant assay (ELISA) are commonly used to monitor various inflammatory and neoplastic disorders associated with lymphocytic proliferation and activation. The in vivo structure of this soluble receptor species, however, is not characterized. We investigated sera with elevated sIL-2R serum levels of patients with histologically proven cutaneous T cell lymphoma (CTCL) and high-dose IL-2-treated melanoma patients and healthy donors. Purified recombinant IL-2R alpha and beta chain molecules, produced by transfection of NIH/3T3 fibroblasts and CHO cells, served as positive controls for purification and detection procedures. For selective enrichment of IL-2R molecules from supernatants and sera, affinity columns were prepared by coupling recombinant IL-2 or monoclonal antibodies against the alpha and the beta chain of the IL-2R complex to cyanogen bromide-activated Sepharose. Western blotting with affinity-purified fractions under reducing and nonreducing conditions revealed proteins that showed immunoreactivity for IL-2R alpha, beta, and gamma chain using several detection antibodies against these molecules. We conclude that the composition of sIL-2R in vivo is more complex than that of recombinant sIL-2R and can include all three IL-2R chains.

Antineoplastic Agents↗

PubMed1992

Soluble interleukin-2 receptors inhibit interleukin 2-dependent proliferation and cytotoxicity: explanation for diminished natural killer cell activity in cutaneous T-cell lymphomas in vivo?

In patients with cutaneous T-cell lymphomas (CTCL), soluble interleukin-2 receptor serum levels (sIL-2R) were determined by ELISA technique, and natural killer cell (NK) activity, by a 4-h chromium-51 release assay. Decrease of NK activity correlated with the augmentation of serum sIL-2R. After a 4-d stimulation with interleukin 2 CTCL patients' peripheral mononuclear cells (PMC) showed an increase of cytotoxic activity similar to that in healthy donors' PMC. Normal donors' PMC demonstrated a diminished IL-2-induced cytotoxic activity in 25% CTCL serum (sIL-2R of 3000, 7330, and 10700 U/ml, respectively) compared to control serum (sIL-2R of 400, 340, and 420 U/ml, respectively). IL-2-dependent proliferation of 2-d phytohemagglutinin (PHA) blasts was lower in CTCL serum than in control serum. sIL-2R was enriched from one CTCL patient's serum by IL-2 affinity chromatography. Transfection of the Tac gene into NIH/3T3 fibroblasts resulted in the production of a recombinant sIL-2R. The presence of enriched native or recombinant sIL-2R inhibited interleukin-2-dependent generation of cytotoxic activity and PHA blast proliferation. We suggest that elevated sIL-2R levels account for diminished NK activity by neutralizing interleukin 2 in CTCL patients.

Cytotoxicity, Immunologic↗

PubMed1989

Binding of steroid receptors to the HREs of mouse mammary tumor virus, chicken and xenopus vitellogenin and rabbit uteroglobin genes: correlation with induction.

Binding to hormone responsive elements (HRE) is an essential step in gene regulation by steroid hormones. Using a combination of in vivo and in vitro studies we have analyzed the interactions of the estrogen receptor with genes from three different systems: the long terminal repeat (LTR) of the mouse mammary tumor virus (MMTV), the chicken and xenopus vitellogenin genes and the rabbit uteroglobin gene. The estrogen receptor binds to all four genes in vitro, but the MMTV LTR does not respond to estrogen in gene transfer experiments. Similarly, the xenopus vitellogenin gene binds the progesterone and glucocorticoid receptors in vitro, but only estrogen induces the xenopus vitellogenin gene in gene transfer. These results suggest that events distal to DNA binding are essential for transcriptional activation, and that the function of the HRE is not simply to position the hormone receptor in the vicinity of the regulated promoter.

Animals↗

PubMed1988

Sequences downstream of the glucocorticoid regulatory element mediate cycloheximide inhibition of steroid induced expression from the rat alpha 1-acid glycoprotein promoter: evidence for a labile transcription factor.

The glucocorticoid induction of alpha 1-acid glycoprotein (AGP) RNA in rat hepatoma cells is diminished by inhibiting protein synthesis. We now show that the AGP 5'-flanking region contains a DNA sequence (position -121 to -107), exhibiting a high degree of homology to the glucocorticoid regulatory element (GRE) consensus sequence ACAXXXTGTTCT, which serves to specifically bind purified rat glucocorticoid receptor in vitro. A 15 base pair oligonucleotide representing the AGP GRE confers glucocorticoid responsiveness on a heterologous promoter; such regulation is not diminished by concurrent inhibition of protein synthesis. However, inclusion of the AGP sequences immediately downstream of the AGP GRE (position -106 to -42) renders the hormonal induction sensitive to inhibition of protein synthesis. Furthermore, inclusion of these downstream sequences results in a more pronounced induction mediated by the AGP GRE. In vitro DNase-1 treatment using nuclear extracts prepared from HTC hepatoma cells generate footprints that indicate the presence of DNA-protein interactions spanning the region from -110 to -68 of the AGP gene. We propose that one or more labile factors acting within this domain, immediately downstream of the GRE, is required for efficient transcription at the AGP promoter.

Animals↗

PubMed1986

Glucocorticoid responsiveness of the transcriptional enhancer of Moloney murine sarcoma virus.

The long terminal repeat of Moloney Murine Sarcoma Virus (MoMSV) contains an imperfect direct repeat that serves as a strong transcriptional enhancer. The strength of the MoMSV enhancer is strongly dependent on the presence of glucocorticoid hormone. Mapping studies in combination with DNAase I footprinting experiments define the presence of glucocorticoid regulatory elements at the promoter-proximal ends of each enhancer repeat. These elements behave like inducible enhancers: their regulatory activity is independent of position and orientation when they are linked in cis to a heterologous promoter. These data demonstrate the modular nature of the MoMSV enhancer and identify the glucocorticoid receptor as one of the trans-acting factors that interact with the MoMSV enhancer and mediate its transcriptional activity.

Animals↗

PubMed1985

Restriction endonucleases in Azospirillum.

Azospirillum brasilense, A. amazonense, and A. lipoferum strains were screened for restriction endonucleases using phage lambda DNA. The extract of A. brasilense 29711 cleaved lambda DNA into specific fragments. It was concluded that this strain possesses a class II restriction endonuclease which was named AbrI. AbrI has a single recognition site on lambda DNA at position of approx. 33 500 bp. AbrI was characterized as an isoschizomer of XhoI, which cuts lambda DNA at 33 498 bp and cleaves double-stranded DNA at the sequence 5'-C TCGAG-3'. From other Azospirilla strains only A. amazonense QRZ42 extracts (AamI activity) cleaved DNA into specific fragments under certain conditions.

Bacteriophage lambda↗