Publications by authors named "Giebel L"

Prolonged exposure to interferon-gamma (IFNγ) and the associated increased expression of the enzyme indoleamine 2,3-dioxygenase 1 (IDO1) create an intracellular shortage of tryptophan in the cancer cells, which stimulates ribosomal frameshifting and tryptophan to phenylalanine (W>F) codon reassignments during protein synthesis. Here, we investigated whether such neoepitopes can be useful targets of adoptive T cell therapy. Immunopeptidomic analyses uncovered hundreds of W>F neoepitopes mainly presented by the HLA-A24:02 allele.

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Deficiencies in the BRCA1 tumor suppressor gene are the main cause of hereditary breast and ovarian cancer. BRCA1 is involved in the Homologous Recombination DNA repair pathway and, together with BARD1, forms a heterodimer with ubiquitin E3 activity. The relevance of the BRCA1/BARD1 ubiquitin E3 activity for tumor suppression and DNA repair remains controversial.

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Perturbation of protein phosphorylation represents an attractive approach to cancer treatment. Besides kinase inhibitors, protein phosphatase inhibitors have been shown to have anti-cancer activity. A prime example is the small molecule LB-100, an inhibitor of protein phosphatases 2A/5 (PP2A/PP5), enzymes that affect cellular physiology.

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The extracellular ligand-binding domain (EPObp) of the human EPO receptor (EPOR) was expressed both in CHO (Chinese Hamster Ovary) cells and in Pichia pastoris. The CHO and yeast expressed receptors showed identical affinity for EPO binding. Expression levels in P.

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Erythropoietin (EPO) stimulates proliferation and differentiation of erythroid progenitor cells. Several lines of evidence indicate that the most likely mechanism of EPO receptor (EPO-R) activation by EPO is homodimerization of the receptor on the surface of erythrocyte precursors. Therefore, we argued that it should be possible to raise EPO-R monoclonal antibodies (MoAbs) that would activate the receptor by dimerization and thus mimic EPO action.

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Human growth hormone binds two receptor molecules and thereby induces signal transduction through receptor dimerization. At high concentrations, growth hormone acts as an antagonist because of a large difference in affinities at the respective binding sites. This antagonist action can be enhanced further by reducing binding in the low affinity binding site.

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We have probed the interaction of human erythropoietin (EPO) with its receptor (EPO-R) by analyzing a panel of 17 EPO mutants in a variety of in vitro assays. Mutant proteins were expressed in 293s cells and quantified by using an N-terminal epitope tag in conjunction with a surface plasmon resonance assay. Receptor binding was studied using both a soluble form of the EPO-R extracellular domain in an ELISA-format binding competition assay and full-length EPO-R in transfected BaF3 cells.

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The screening of combinatorial peptide libraries has emerged as an important tool in the discovery of novel substrates or ligands for enzyme and receptor targets. For example, screening linear peptide libraries using streptavidin as a model receptor system has previously identified many low-affinity peptide ligands, all of which contain the common motif His-Pro-Gln (HPQ). We reasoned that constraining the conformational freedom of linear peptides by cyclization in a library would yield peptide ligands of increased affinity.

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We have cloned and sequenced the human KIT proto-oncogene, which contains 21 exons and spans more than 34 kb of DNA on chromosome segment 4q12. We also establish physical linkage between the KIT gene and the related PDGFRA gene. The organization of the KIT gene is virtually identical to that of the homologous FMS gene, located on chromosome 5.

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Type I (tyrosinase-deficient) oculocutaneous albinism (OCA) results from mutations of the gene encoding tyrosinase, the enzyme that catalyzes the first 2 steps of melanin pigment biosynthesis. In type IA (tyrosinase-negative) OCA tyrosinase enzymatic activity is completely absent, and in type IB ("yellow") OCA tyrosinase activity is greatly reduced. Here, we describe 11 novel mutations of the tyrosinase gene in Caucasian patients with these 2 forms of type I OCA.

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Piebaldism is an autosomal dominant disorder of melanocyte development and is characterized by congenital white patches of skin and hair from which melanocytes are completely absent. A similar disorder of the mouse, "dominant white spotting" (W), results from mutations of the c-kit proto-oncogene, which encodes the cellular tyrosine kinase receptor for the mast/stem cell growth factor. We have identified c-kit gene mutations in three patients with piebaldism.

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Piebaldism is an autosomal dominant genetic disorder characterized by cogenital patches of skin and hair from which melanocytes are completely absent. A similar disorder of mouse, dominant white spotting (W), results from mutations of the c-Kit protooncogene, which encodes and receptor for mast/stem cell growth factor. We identified a KIT gene mutation in a proband with classic autosomal dominant piebaldism.

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We detected a nonsense mutation in the tyrosinase gene of two Afghan sibs with classical tyrosinase negative (type IA) oculocutaneous albinism. The mutation, a single base substitution at codon 178, creates an amber termination codon that truncates the 529 amino acid tyrosinase polypeptide at this position. The patients' parents are first cousins, and the patients are therefore homoallelic for this mutation.

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We have identified three different tyrosinase gene mutant alleles in four unrelated patients with type IB ("yellow") oculocutaneous albinism (OCA) and thus have demonstrated that type IB OCA is allelic to type IA (tyrosinase negative) OCA. In an inbred Amish kindred, type IB OCA results from homozygosity for a Pro----Leu substitution at codon 406. In the second family, type IB OCA results from compound heterozygosity for a type IA OCA allele (codon 81 Pro----Leu) and a novel type IB allele (codon 275 Val----Phe).

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We have identified a common nonpathological polymorphism of the human tyrosinase gene. In Caucasians codon 402 can be either CGA (arginine) [p = .85] or CAA (glutamine) [p = .

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The genetic characterization of a serologically Hantaan-like virus but of unknown origin (termed DX) was carried out by molecular cloning and nucleotide sequencing of the corresponding cDNA of the viral S RNA segment. The S RNA was found to be 1765 nucleotides long with 3' and 5' termini being complementary for 24 bases. The virus messenger-sense RNA contains one major open reading frame (ORF) encoding 428 amino acids or a 50 kD polypeptide.

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We have isolated and sequenced the gene encoding human tyrosinase, the key enzyme in pigment biosynthesis. The human tyrosinase gene contains five exons and spans more than 50 kb of DNA on chromosome segment 11q14----q21. We have also isolated a second segment in the human genome that is closely related to tyrosinase.

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Type I oculocutaneous albinism (OCA) is an autosomal recessive disorder in which deficient synthesis of melanin pigment results from abnormal activity of melanocyte tyrosinase. A novel type I OCA phenotype in which hypopigmentation is related to local body temperature is associated with a missense substitution in tyrosinase, codon 422 CGG (Arg)----CAG (Gln). This substitution results in a tyrosinase polypeptide that is temperature-sensitive.

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The polymerase chain reaction (PCR) with subsequent nucleotide sequence analysis was employed to rapidly detect genomic variations among different Hantavirus strains. Using synthetic oligonucleotide primers derived from the M and S segment RNAs of nephropathia epidemica virus strain Hällnäs B1 (NEV) we succeeded in amplifying the corresponding sequences of Hantaan and Puumala viruses. The nucleotide sequences of the cDNAs derived from the Puumala M and S RNA segments were analyzed.

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We have identified a tyrosinase gene mutation in several patients with classic, tyrosinase-negative (type IA) oculocutaneous albinism. This mutation, which results in a proline----leucine substitution at codon 81 of the tyrosinase polypeptide (EC 1.14.

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