Biomedical subjects

T Spies

Publications and source records attributed to T Spies.

79 records · Page 5Linked to original sources

PubMed1985

Gene organization of DC and DX subregions of the human major histocompatibility complex.

The DC and DX subregions of the human major histocompatibility complex (MHC) have been cloned from a cosmid library made from a human B-cell line, Priess. The DC subregion, 48 kilobases, includes the DC alpha and DC beta genes. A second DC-like region, the DX subregion, 35 kilobases, contains the DX alpha gene and a newly found beta gene termed DX beta. Since the DC and DX genes are highly homologous in nucleotide sequence, gene size, exon-intron organization, and direction of transcription, the DC and DX subregions were presumably generated by duplication of an ancestral alpha-beta gene pair. Nucleotide sequencing indicates that all four genes have intact coding sequences and promoter regions. Homology between the upstream promoter sequences of these four genes and seven other class II genes at nucleotides -69 to -78 and -98 to -110 highlights these previously described conserved elements. Moreover, a striking conservation of flanking alpha-gene-specific and beta-gene-specific sequences has been observed. Comparison of Southern blots of Priess DNA with DC alpha and DC beta cDNA probes with isolated cosmid clones showed that (i) the human chromosome encodes only two DC alpha-related and two DC beta-related genes, namely, DC alpha, DX alpha, DC beta, and DX beta, and (ii) the DC and DX subregions are homozygous in Priess cells.

Chromosome Mapping↗

PubMed1985

Structural organization of the DR subregion of the human major histocompatibility complex.

Two clusters of overlapping cosmid and lambda phage clones comprising 205 kilobases (kb) have been isolated from the DR subregion of the human major histocompatibility complex from a DR4 haplotype. A single DR alpha and three DR beta genes were identified. In one cluster (135 kb), the DR alpha gene is 90 kb distant from the DR beta gene encoding a molecule that carries the MT3 serological specificity. In the second cluster (70 kb), the DR beta gene determining the DR4 specificity is located 22 kb apart from a DR beta pseudogene (DR beta psi). A 3- to 4-kb sequence located at the 5' end of the DR beta (MT3) gene is common to all three DR beta-chain genes. In addition, three more copies of this sequence are spaced between the DR alpha and the DR beta (MT3) genes in the first cluster and one of these, at least, is associated with a DR beta 1 exon, suggesting that additional genes could be encoded in this region and that multiple duplication events have led to its evolution.

Biological Evolution↗

PubMed1985

Genetic complexity and expression of human class II histocompatibility antigens.

The genes encoding nearly all of the serologically defined class II antigens of the major histocompatibility complex have been isolated. Three class II loci have been studied in great detail. The DR region contains a single alpha gene and 3 beta chain genes, 1 of which is a pseudogene. The DR alpha chain gene has been linked to a DR beta gene which encodes a beta protein which contains the serological determinant MT3. A second cosmid cluster contains 2 beta genes, 1 of which encodes the DR4 allospecificity. The identification of these genes has been made by the comparison of amino terminal sequences of DR molecules obtained from a DR4 cell line and the deduced protein sequences of the beta 1 exons from cosmid and phage clones. A conserved element including the promoter and signal sequence is found at the 5' end of each of the 3 DR beta genes. Additionally, this element occurs three more times in the DR region, raising the question of whether additional beta chain genes might be found. The DQ region contains 2 pairs of genes, 1 of which encodes the DQ antigen. The 2nd pair of genes, called DX alpha and beta, appears to be capable of expressing a DQ-related product, although, to date, there is no evidence for its expression. The DP region also contains 2 pairs of genes. One pair encodes the DP antigen while the 2nd alpha-beta pair is shown to be composed of pseudogenes. The location of polymorphic regions in these genes and aspects of their relationship to the serology, evolution, and function of the class II MHC are discussed. The control of expression of class II genes by gamma-interferon has been examined. The promoters of class II genes are characterized by two conserved sequences common to all alpha and beta chain genes as well as by conserved sequences specific for either alpha or beta chain genes. In addition to studies of expression by DNA-mediated gene transformation, a system for the gene transfer of MHC antigens utilizing transmissible retrovirus vectors is described. Retrovirus vectors have been used to transmit DR alpha, DR beta, and the invariant chain (gamma) sequences to recipient cells with resultant expression of these proteins.

Alleles↗

PubMed1983

Amplification of resistance genes in Haemophilus influenzae plasmids.

Intramolecular amplification produces tandem repeats of tetracycline and combined tetracycline-chloramphenicol resistance determinants in conjugative plasmids of Haemophilus influenzae. This process depends on host recombination pathways. Physical mapping revealed the tetracycline transposon involved in amplification to be almost identical with Tn10, including two IS10 insertion elements. The chloramphenicol resistance determinant of the combined transposon is 1.9 kilobases (kb) in size and is bound by two 1.3-kb inverted repeats. Insertion in the close vicinity of the inside end of the left-hand IS10 generates a deletion of a 1.6-kb Tn10 region. The amplifiable units were resolved to comprise not only the respective resistance transposons, but also an additional 1.6-kb sequence (designated AS) which was demonstrated to be identically present in the different amplification systems studied. AS separates amplified transposons from each other, thereby maintaining the same orientation. Moreover, AS is present at the left flank of the transposons, but is missing at the right one. It was shown that AS represents a general constituent of the H. influenzae plasmids of the 45-kb class. Evaluation of the results suggests that AS is responsible for the recombinational events involved in the gene amplification process.

Chloramphenicol↗

PubMed1983

Circularized copies of amplifiable resistance genes from Haemophilus influenzae plasmids.

Tandem repeat amplification of resistance determinants in Haemophilus influenzae plasmids is associated with the occurrence of separate circular DNA molecules. They were demonstrated to represent mono- and multimeric forms of the amplifiable segments of the plasmids which comprise the respective resistance transposons and an additional region designated as an amplification sequence. The latter region mediates the recombinational events involved in amplification. The DNA circles apparently lack the ability to replicate autonomously but most probably provide an effective means for the translocation of resistance genes from one plasmid to another.

DNA Restriction Enzymes↗

PubMedDate not supplied

Interactions of human NKG2D with its ligands MICA, MICB, and homologs of the mouse RAE-1 protein family.

NKG2D is an activating receptor that is expressed on most natural killer (NK) cells, CD8 alphabeta T cells, and gammadelta T cells. Among its ligands is the distant major histocompatibility complex class I homolog MICA, which has no function in antigen presentation but is induced by cellular stress. To extend previous functional evidence, the NKG2D-MICA interaction was studied in isolation. NKG2D homodimers formed stable complexes with monomeric MICA in solution, demonstrating that no other components were required to facilitate this interaction. MICA glycosylation was not essential but enhanced complex formation. Soluble NKG2D also bound to cell surface MICB, which has structural and functional properties similar to those of MICA. Moreover, NKG2D stably interacted with surface molecules encoded by three newly identified cDNA sequences (N2DL-1, -2, and -3), which are identical to the human ULBP proteins and may represent homologs of the mouse retinoic acid-early inducible family of NKG2D ligands. Because of the substantial sequence divergence among these molecules, these results indicated promiscuous modes of receptor binding. Comparison of allelic variants of MICA revealed large differences in NKG2D binding that were associated with a single amino acid substitution at position 129 in the alpha2 domain. Varying affinities of MICA alleles for NKG2D may affect thresholds of NK-cell triggering and T-cell modulation.

Amino Acid Sequence↗

PubMedDate not supplied

A gene in the human major histocompatibility complex class II region controlling the class I antigen presentation pathway.

Major histocompatibility complex (MHC) class I molecules export peptides to the cell surface for surveillance by cytotoxic T lymphocytes. Intracellular peptide binding is critical for the proper assembly and transport of class I molecules. This mechanism is impaired as a result of a non-functional peptide supply factor gene (PSF) in several human mutant cell lines with genomic lesions in the MHC. We have now identified PSF in the MHC class II region by deletion mapping in mutants and chromosome-walking. PSF is homologous to mammalian and bacterial ATP-dependent transport proteins, suggesting that it operates in the intracellular transport of peptides.

Amino Acid Sequence↗