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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Expression of a mammalian major histocompatibility complex (MHC) class I gene is in part regulated by a silencer DNA sequence element which binds a complex of silencer factors. This negative regulatory system is shown to be strikingly similar to the yeast alpha 2 mating-type repression system. A moderate DNA sequence homology exists between the MHC class I silencer DNA element and the yeast alpha 2 operator. Mammalian silencer factors specifically bind to the yeast alpha 2 operator DNA and also specifically interact with a yeast alpha 2-binding protein. Furthermore, the alpha 2 operator functions as a silencer element in mammalian cells when placed upstream of a MHC class I promoter.
Mol Cell Biol 1991 Aug
PMID:Striking similarities between the regulatory mechanisms governing yeast mating-type genes and mammalian major histocompatibility complex genes. 207 16

H-2L-null variants were immunoselected from a transfected murine fibroblast cell line carrying a single copy H-2L gene, and were characterized to determine the basis for the loss of this MHC class I cell surface product. Molecular analysis indicated that inactivation of H-2L expression in nearly every null clone resulted from an apparent deletion or rearrangement of 5'-flanking and 5'-coding H-2L sequences, with breakpoints consistently mapping to within a 550 bp GC-rich region between exon 1 and the middle of intron 2. Notably, this region of the H-2L gene contains a large number of overlapping, inverted repeat sequences as well as potential topoisomerase I cleavage sites. Examination of several in vivo mutant class I genes, believed to have been generated by recombination, has revealed that each of these genes bears similar palindromic structures overlapping or adjacent to the regions of sequence exchange. These findings suggest that inverted repeat sequences may play a role in recombination and deletion within the MHC class I multigene family.
Mol Immunol 1990 Sep
PMID:Overlapping palindromic sequences associated with somatic deletion and meiotic recombination of MHC class I genes. 217 Aug 32

The functional importance of various cell membrane bound molecules was studied and compared in the NK cytotoxicity and CTL activity. LFA-1 and CD2 participate in both killing functions, while CD3 and CD8/CD4 as well as MHC class I molecules are involved only in CTL activity. Nevertheless CD2- and beta 2-microglobulin are representatives of the NK function. It was demonstrated that CD2-, LFA-1 and beta 2-microglobulin molecules have an additive and complementary function in the killing mechanism. The upregulation of alpha- and gamma-interferons on NK function seems not to be a consequence of the enhanced expression of these molecules on the cell surface induced by IF at the same time.
Mol Immunol 1986 Nov
PMID:Regulatory function of cell surface molecules CD2-, LFA- and beta 2-microglobulin in natural killer cell activity. 243 40

Membranes were isolated from B cells stimulated with phorbol 12-myristate 13-acetate (PMA) for a time sufficient to allow maximal redistribution and activation of protein kinase C (PKC). Exposure of such membranes to a short incubation with [gamma-32P]ATP resulted in the detection of at least nine unique or hyperphosphorylated membrane proteins by SDS-PAGE and autoradiography. The appearance of these phosphoproteins was blocked by pretreatment of the membranes with H-7 or sangivamycin, two selective inhibitors of PKC. In addition, membranes purified from B cells treated with an inactive phorbol ester or stimulated with dibutyryl cAMP failed to exhibit a pattern of new phosphoproteins. These results are consistent with the involvement of PKC in the phosphorylation of the proteins. These phosphoproteins are also candidates for proteins whose functions are modified as a consequence of early signal delivery to resting B cells following membrane immunoglobulin occupancy. This system was utilized to identify the heavy chain of MHC class I molecules as one of the membrane proteins phosphorylated by PKC. The MHC class II molecules were not phosphorylated in membranes isolated from PMA-treated normal B cells or from PMA-treated B cells which had previously been exposed to IL-4. These results indicate that class I, but not class II, MHC molecules are phosphorylated by PKC. It is possible that such a modification of cell surface class I molecules may be involved during the process of signal transduction leading to B cell activation.
Mol Immunol 1989 Dec
PMID:Phosphorylation of class I but not class II MHC molecules by membrane-localized protein kinase C. 263 45

By varying growth conditions, we identified a novel mechanism of autocrine regulation of major histocompatibility complex (MHC) class I gene expression by induction of beta interferon gene expression in transformed BALB/c-3T3 cells. Low-serum conditions enhanced MHC class I antigen expression in v-rasKi- and v-mos-transformed BALB/c-3T3 cells but not in untransformed BALB/c-3T3 cells. Transformed and untransformed cells grown under standard serum conditions (10% bovine calf serum) expressed similar cell surface levels of MHC class I antigens. However, low-serum conditions (0.5% bovine calf serum) induced four- to ninefold increases in cell surface levels of MHC class I antigens in both v-rasKi- and v-mos-transformed cells but not in untransformed cells. These increases in MHC class I gene expression were seen at both the mRNA and cell surface protein levels and involved not only the heavy-chain component of the class I antigens but also beta 2 microglobulin. Beta 1 interferon mRNA and beta interferon-inducible 2',5'-oligoadenylate synthetase mRNA were induced by growth under low-serum conditions in transformed BALB/c-3T3 cells, and antibodies to beta interferon blocked the induction of MHC class I antigen expression by serum deprivation in these cells. These results demonstrate that growth under low-serum conditions leads to induction of beta interferon expression in oncogene-transformed cells which then directly mediates autocrine enhancement of MHC class I gene expression.
Mol Cell Biol 1989 May
PMID:Autocrine induction of major histocompatibility complex class I antigen expression results from induction of beta interferon in oncogene-transformed BALB/c-3T3 cells. 266 64

Cytotoxic T lymphocytes (CTL) recognize antigen in the context of syngeneic MHC class I gene products. The "learning" of MHC restriction is thought to take place during the early intrathymic development of cytotoxic lymphocyte precursors (CLP). This view does not allow for any significant number of "allorestricted" (as opposed to selfrestricted) T cells to occur among mature, peripheral T cells. Recent evidence indicates, however, that large numbers of antigen-specific, allorestricted CLP can be readily detected among splenic T cell populations from several strains of unprimed normal mice. The frequencies of allorestricted CLP as determined under limiting dilution (LD) culture conditions are in fact in the same order of magnitude as frequencies of selfrestricted CLP. These findings were at the origin of the present study, which was designed to investigate whether antigen-specific, allorestricted CTL populations could also be detected among human peripheral blood T lymphocytes. To address this issue we studied the CTL response to virus-infected allogeneic stimulator cells in two different LD systems. In the first system, peripheral T cells from normal donors were cocultured under precisely defined LD conditions with Epstein-Barr virus (EBV)-transformed allogeneic lymphoblastoid cell lines (LCL). Frequencies of CLP that lysed the stimulating LCL ranged from one in 70 to one in 200, while frequencies of CLP that lysed the respective allogeneic ConA blast targets were 3-40-fold lower. The split-well analysis suggested that a large fraction of developing CTL colonies specifically lysed the stimulating LCL targets but neither the respective ConA blasts nor HLA-mismatched third party LCL targets. CTL generated in this culture system thus displayed allorestricted specificity for LCL membrane antigens. Comparable results were obtained in a second LD system where T cells from normal donors were cocultured with mumps virus-infected allogeneic mononuclear cells (MNC) or ConA blasts. One of 600 to one of 2,800 T cells gave rise to a cytotoxic colony that lysed mumps virus-infected stimulator-derived ConA blast target cells. To assess the lytic specificity of the in vitro expanding CTL populations, individual microcultures were split into three aliquots and tested for cytolytic activity against mumps virus-infected and noninfected specific targets as well as mumps virus-infected, HLA-mismatched third party targets. Clonal CTL populations from four of seven donors lysed virus-infected stimulator targets but did not lyse either noninfected stimulator targets or mumps virus-infected third party targets, i.e., they again showed an antigen-specific allorestricted lytic r
J Mol Cell Immunol 1987
PMID:Human cytotoxic T lymphocytes. III. Large numbers of peripheral blood T cells clonally develop into allorestricted anti-viral cytotoxic T cell populations in vitro. 285 6

The role of the immune system in the central nervous system has been elusive. Our original description of Ia bearing cells in the central nervous system was controversial, although it has now been confirmed in a variety of systems in both mouse and humans. The function of Ia bearing cells is however still unclear. Recently, others have shown that astrocytes from rats with EAE could present myelin basic protein to T cell clones; however, no other antigens were tested. We have used the culture systems of McCarthy and DeVellis to produce purified cultures of astrocytes and oligodendroglial cells from newborn mouse brains. Newborn brains were chosen since it is impossible to obtain pure cultures of differentiated brain cells from adult mice. Using these cultures, we showed that astrocyte, but not oligodendrocyte cultures treated with ConA supernatants or recombinant IFN-gamma are able to present antigen to appropriate but not inappropriate T cell hybrids. Untreated cells of either the astrocyte or oligodendroglial cell populations were ineffective at antigen presentation. Concomitant with this increase in antigen presenting ability, follows an increase in both the number and density of MHC class I and class II antigens. Antigen presentation was inhibited by appropriate but not inappropriate anti Ia monoclonal antibodies. Anti class I antibodies were ineffective. Depletion experiments showed that both I-A and I-E molecules are expressed on the antigen presenting cells. Thus, we have been able to show that Ia+ cells derived from pure cultures of astrocytes are able, after induction with IFN-gamma, to present antigen to T cell hybrids. This suggests a possible physiologic role of Ia bearing cells in CNS in initiation of immune responses.
J Mol Cell Immunol 1986
PMID:Induction of antigen presentation ability in purified cultures of astroglia by interferon-gamma. 315 Oct 59

Nucleotide sequence analysis of mRNA from the H-2K locus of the CBA.M523 mouse, which has the class I murine MHC mutation H-2Kkml, has established the only alteration to be at the codon for amino acid position 152 as compared to the sequence of standard Kk from both the AKR and CBA inbred mouse lines. Complete sequence information for the nucleotides coding for amino acids 1-292, which includes all of the extracellular protein domains, demonstrated an A----C alteration in the codon for amino acid 152 as compared to the standard Kk sequence, changing Asp (GAT) in Kkml. The GCT codon occurring in Kkml may be the result of a gene conversion in Kkml. The GCT codon occurring in Kkml may be the result of a gene conversion event because a potential donor gene, the pH-2III pseudogene of H-2k, is transcribed in the CBA.M523 mouse and has a GCT codon at amino acid position 152. This sequence information obtained for Kkml also demonstrates that Kk gene transcripts from two genetically distinct inbred mouse lines, CBA and AKR, are completely identical. Finally, several other murine and human class I MHC variants have similar alterations at amino acid position 152 which result in altered biological functions. This information suggests that amino acid 152 is an important part of a T-cell-recognized antigenic determinant on MHC class I antigens.
Mol Immunol 1988 Mar
PMID:The H-2Kkml mutation: a single nucleotide substitution is responsible for multiple functional differences in a class I MHC molecule. 337 94

Chicken and turkey beta 2-m were isolated from citrated plasma in sequential use of three chromatographic steps: affinity chromatography, gel filtration chromatography and anion-exchange chromatography. The purified protein was identified as beta 2-m by reaction with a beta 2-m specific monoclonal antibody and by the ability to recombine with the chicken MHC class I heavy chain. The purity was estimated by SDS-PAGE and IEF. The pI was between 5.1 and 5.3 for chicken beta 2-m and 4.7 and 4.8 for turkey beta 2-m, which fact is reflected in their different electrophoretic mobilities in agarose gel (turkey migrates in the alpha and chicken migrates in the beta region). The mol. wt of both chicken and turkey beta 2-m was 14,500 estimated by SDS-PAGE whereas calculations based on the amino acid compositions gave mol. wts of 11,000. EM280 was 15.9 for chicken beta 2-m and 16.4 for turkey beta 2-m. The amino acid compositions and sequences of the two avian beta 2-m molecules have been compared with earlier data from the literature. The sequence of the 23 N-terminal amino acids was found to be identical in our preparations from both chicken and turkey, namely DLTPKVQVYSRFPASAGTKNVLN, and is incompatible with a previously published sequence also thought to be from turkey beta 2-m. Reasons for our opinion that the molecules isolated and sequenced in this paper are the correct ones are given.
Mol Immunol 1986 Dec
PMID:Isolation and characterization of chicken and turkey beta 2-microglobulin. 354 90

Relative affinities were determined for the interaction of H-2Db with all the peptides from the A/PR/8/34 strain of influenza virus that contained the Db-binding motif. The results indicated that, even though 23 peptides with the appropriate motif were identified and analysed, binding of only five of them could be detected at peptide concentrations lower than 10(-7) M. Of these five, only one, TGICNQNII, bound with better affinity than the nucleoprotein-derived natural epitope, ASNENMETM. The origin of the higher binding peptide was the influenza neuraminidase, a protein for which little cytosolic processing would be expected since it is a surface glycoprotein. To establish why many of the influenza-derived peptides did not bind, the role of non-anchor residues on Db-peptide interactions was analysed, using a scheme where QDIENEEKI, a non-binding peptide from the influenza virus polymerase 1, was sequentially converted to ASNENMETI, which binds to Db with an affinity similar to that of ASNENMETM. Although all positions examined influenced peptide binding, peptide residue no. 2 (P2) was of particular importance. Therefore, each of the 20 naturally occurring amino acids were inserted at this position to investigate their effects on peptide-MHC interaction. The results indicated that amino acids having side chains with charged or ring structures were deleterious, while non-polar and polar residues were either neutral or facilitated binding to different degrees. Our data also indicated that every residue of the peptide contributes to the stability of the MHC-peptide complex, and the final affinity is dependent on the nature of the amino acids at each position, not just on those at a small number of anchor positions. The results also suggested that increased stability, as indicated by the half-life of the peptide-MHC class I complex, might play an important role in selecting the immunodominant epitope.
Mol Immunol 1995 Jun
PMID:Db-binding peptides from influenza virus: effect of non-anchor residues on stability and immunodominance. 764 54


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