Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “mutual exclusivity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed1997

Regulation of gene expression by repressor localization: biochemical evidence that membrane and DNA binding by the PutA protein are mutually exclusive.

The PutA protein from Salmonella typhimurium is a bifunctional enzyme that catalyzes the oxidation of proline to glutamate, a reaction that is coupled to the transfer of electrons to the electron transport chain in the cytoplasmic membrane. The PutA protein is also a transcriptional repressor that regulates the expression of the put operon in response to the availability of proline. Despite extensive genetic and biochemical studies of the PutA protein, it was not known if the PutA protein carries out both of these two opposing functions while membrane associated or if instead it carries them out in different cellular compartments. To distinguish between these alternatives, we directly assayed the binding of purified PutA protein to DNA and membranes in vitro. The results indicate that wild-type PutA does not simultaneously associate with DNA and membranes. In addition, PutA superrepressor mutants that exhibit increased repression of the put genes show a direct correlation between decreased membrane binding and increased DNA binding. These results support a model in which the PutA protein shuttles between the membrane (where it acts as an enzyme but lacks access to DNA-binding sites) and the cytoplasm (where it binds DNA and acts as a transcriptional repressor), depending on the availability of proline.

Bacterial Proteins↗
PubMed2001

Mutually exclusive distribution of IS1548 and GBSi1, an active group II intron identified in human isolates of group B streptococci.

The present study shows that active, self-splicing group II intron GBSi1 is located downstream of the C5a-peptidase gene, scpB, in some group B streptococcus (GBS) isolates that lack insertion sequence IS1548. IS1548 was previously reported to be often present at the scpB locus in GBS isolated in association with endocarditis. Since none of 67 GBS isolates examined, 40 of which were of serotype III, harbored both IS1548 and GBSi1, these two elements are suggested to be markers for different genetic lineages in GBS serotype III. The DNA region downstream of scpB in GBS isolates harboring either GBSi1, IS1548, or none of these mobile elements was found to encode the laminin binding protein, Lmb, which shows sequence similarities to a family of streptococcal adhesins. IS1548 is inserted 9 bp upstream of the putative promoter for lmb, while the insertion site for GBSi1 is located 88 bp further upstream. Sequences highly similar to GBSi1 exist also in Streptococcus pneumoniae. An inverted repeat sequence, with features typical of transcription terminators, was identified immediately upstream of the insertion site for the group II intron both in the GBS and S. pneumoniae sequences. This motif is suggested to constitute a target for the GBS intron as well as for rather closely related introns in Bacillus halodurans, Pseudomonas alcaligenes, and Pseudomonas putida. When transcripts containing the GBSi1 intron were incubated at high concentrations of ammonium and magnesium, a major product with the expected length and sequence for the ligated exons was generated. Unlike, however, all members of group II investigated so far, the excised intron was in linear, rather than in a branched (lariat), form.

Adhesins, Bacterial↗
PubMed2006

Mutually exclusive T-cell receptor induction and differential susceptibility to human immunodeficiency virus type 1 mutational escape associated with a two-amino-acid difference between HLA class I subtypes.

The relative contributions of HLA alleles and T-cell receptors (TCRs) to the prevention of mutational viral escape are unclear. Here, we examined human immunodeficiency virus type 1 (HIV-1)-specific CD8(+) T-cell responses restricted by two closely related HLA class I alleles, B*5701 and B*5703, that differ by two amino acids but are both associated with a dominant response to the same HIV-1 Gag epitope KF11 (KAFSPEVIPMF). When this epitope is presented by HLA-B*5701, it induces a TCR repertoire that is highly conserved among individuals, cross-recognizes viral epitope variants, and is rarely associated with mutational escape. In contrast, KF11 presented by HLA-B*5703 induces an entirely different, more heterogeneous TCR beta-chain repertoire that fails to recognize specific KF11 escape variants which frequently arise in clade C-infected HLA-B*5703(+) individuals. These data show the influence of HLA allele subtypes on TCR selection and indicate that extensive TCR diversity is not a prerequisite to prevention of allowable viral mutations.

Alleles↗
PubMed1996

EBNA-2 and EBNA-3C extensively and mutually exclusively associate with RBPJkappa in Epstein-Barr virus-transformed B lymphocytes.

Although genetic and biochemical data indicate that the cell protein RBPJkappa is a mediator of EBNA-2 and EBNA-3C effects on transcriptional regulatory elements, the extent of association of these Epstein-Barr virus nuclear proteins with RBPJkappa in transformed B lymphocytes has not been determined. We now report that most of the EBNA-2 and at least 20% of the EBNA-3C coimmunoprecipitated with RBPJkappa from extracts of transformed B lymphocytes that contained most of the cellular EBNA-2 and EBNA3C. Both proteins are associated preferentially with the smaller of the two RBPJkappa isoforms. EBNA-2-RBPJkappa complexes do not contain EBNA-3C, and EBNA-3C-RBPJkappa complexes do not contain EBNA-2. Although EBNA-2 and EBNA-3C are extensively associated with RBPJkappa, a fraction of RBPJkappa appears to be free of EBNAs after repeated immunoprecipitations with anti-EBNA, Epstein-Barr virus-immune, human antibody. Promoters with RBPJkappa sites in their regulatory elements are likely to be differentially regulated by these RBPJkappa-EBNA-2 and RBPJkappa-EBNA-3 complexes.

Antigens, Viral↗
PubMed2006

Insulin-like growth factor I controls a mutually exclusive association of RACK1 with protein phosphatase 2A and beta1 integrin to promote cell migration.

The WD repeat scaffolding protein RACK1 can mediate integration of the insulin-like growth factor I receptor (IGF-IR) and integrin signaling in transformed cells. To address the mechanism of RACK1 function, we searched for regulatory proteins that associate with RACK1 in an IGF-I-dependent manner. The serine threonine phosphatase protein phosphatase 2A (PP2A) was found associated with RACK1 in serum-starved cells, and it dissociated immediately upon stimulation with IGF-I. This dissociation of PP2A from RACK1 and an IGF-I-mediated decrease in cellular PP2A activity did not occur in cells expressing either the serine 1248 or tyrosine 1250/1251 mutants of the IGF-IR that do not interact with RACK1. Recombinant RACK1 could bind to PP2A in vitro and restore phosphatase activity to PP2A from IGF-I-stimulated cells. Ligation of integrins with fibronectin or Matrigel was sufficient to facilitate IGF-I-mediated dissociation of PP2A from RACK1 and also to recruit beta1 integrin as PP2A dissociated. By using TAT-fused N-terminal and C-terminal deletion mutants of RACK1, we determined that both PP2A and beta1 integrin interact in the C terminus of RACK1 within WD repeats 4 to 7. This suggests that integrin ligation displaces PP2A from RACK1. MCF-7 cells overexpressing RACK1 exhibited enhanced motility, which could be reversed by the PP2A inhibitor okadaic acid. Small interfering RNA-mediated suppression of RACK1 also decreased the migratory capacity of DU145 cells. Taken together, our findings indicate that RACK1 enhances IGF-I-mediated cell migration through its ability to exclusively associate with either beta1 integrin or PP2A in a complex at the IGF-IR.

Animals↗
PubMed1994

Psoriasis and eczema are not mutually exclusive diseases.

BACKGROUND: Some reports have suggested that psoriasis and eczema are seldom found together. Knowledge of disease co-occurrence could lead to improved understanding of shared or opposing pathological mechanisms. OBJECTIVE: We sought to determine whether psoriasis and eczema could exist simultaneously and consecutively in the same individuals. METHODS: Skin examination data relating to 9,263 British children born during March 3rd to 9th, 1958 (the National Child Development Survey), were analysed for the co-occurrence of eczema and psoriasis. RESULTS: Of 354 children with visible eczema at the ages of 11 or 16 years, 5 (1.4%) were also noted to have visible psoriasis, compared to 89 (1.0%) of 8,909 children who did not have visible eczema at 11 or 16 years. The relative risk of psoriasis in a case of eczema was 1.41, 95% confidence intervals from 0.58 to 3.46. CONCLUSION: Contrary to some hospital-based studies which have suggested that the two diseases are seldom found together, this study of a large and representative population suggests that eczema and psoriasis may co-occur concurrently and consecutively in the same individual.

Adolescent↗
PubMed1989

Psoriasis and lichen planus: coexistence in a single patient. Are both diseases mutually exclusive?

The coexistence of psoriasis and lichen planus has been rarely reported, although both diseases are relatively common and have some features in common. A rare case of simultaneous occurrence of both diseases is presented. Spontaneous improvement of psoriasis occurred during the development of lichen planus and a subsequent disappearance of the lichen planus was associated with an exacerbation of the psoriasis. The clinical courses of the two diseases may not be independent of each other, but be affected by common factors. Immunohistochemical studies with lesional skin suggested local production of interferon-gamma, which may in part explain the improvement of the psoriasis during the development of lichen planus. Based on these immunohistochemical findings, we discuss a putative role for these lymphokines in the pathogenesis of the two diseases.

Adult↗
PubMed1987

Borderline and schizotypal personality disorders: mutually exclusive or overlapping?

This article is concerned with one aspect of the validity of DSM-III Axis II diagnoses, namely, the discriminability of borderline and schizotypal disorders. Forty-nine patients diagnosed by DSM-III criteria as borderline, schizotypal, or "mixed" personality disorders completed the Borderline Syndrome Index (BSI), an independent self-report 52-item instrument that has been shown to be reliable and to have discriminative validity. A one-way analysis of variance and a discriminant function analysis were conducted. Our major finding was that there were no significant differences among the groups on the BSI self-report test, although there were differences on clinical grounds. We discuss this in terms of "fuzzy set" theory and prototypic systems of classification.

Adult↗
PubMed1992

Mutually exclusive expression of the Strongylocentrotus purpuratus Spec1 gene and its Lytechinus pictus homologue in cells of hybrid embryos.

The expression of the Spec1 gene of Strongylocentrotus purpuratus and its Lytechinus pictus homologue LpS1 was analyzed in reciprocal hybrid embryos of these two species of sea urchin. While the time course of accumulation of Spec1 mRNA was nearly normal in hybrid embryo populations, the accumulation of LpS1 mRNA was not. This was particularly evident in plutei, where the level of LpS1 mRNA was less than 5% that in normal L. pictus plutei. In situ hybridization analysis of serial sections indicated that LpS1 mRNA was detectable in only about 2% of hybrid plutei in either cross, whereas Spec1 mRNA was present in nearly all hybrid plutei; expression of either homologue was appropriately restricted to the aboral ectoderm. In crosses of L. pictus eggs with S. purpuratus sperm (LpSp), about 1% of hybrid plutei expressed LpS1 RNA in most or all aboral ectoderm cells at normal levels, and did not express Spec1 RNA; in another 1% of the LpSp hybrid plutei the Spec1 and LpS1 transcripts were present at normal levels in complementary, non-overlapping patches of contiguous aboral ectoderm cells. In the reciprocal SpLp cross, each hybrid pluteus expressed either only the LpS1 gene (about 2%) or only the Spec1 gene throughout the aboral ectoderm. In SpLp hybrid gastrulae the level of LpS1 mRNA was less restricted; about 2% of the embryos contained only LpS1 RNA, and about half expressed only Spec1 transcripts, but in the remaining embryos Spec1 and LpS1 transcripts were coexpressed in the same aboral ectoderm cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

ARVCF localizes to the nucleus and adherens junction and is mutually exclusive with p120(ctn) in E-cadherin complexes.

ARVCF is a novel Armadillo repeat domain protein that is closely related to the catenin p120(ctn). Using new ARVCF monoclonal antibodies, we have found that ARVCF associates with E-cadherin and competes with p120 for interaction with the E-cadherin juxtamembrane domain. ARVCF also localized to the nucleus in some cell types, however, and was significantly more nucleophilic than p120. Surprisingly, despite apparently ubiquitous expression, ARVCF was at least tenfold less abundant than p120 in a wide variety of cell types, and was difficult to detect by immunofluorescence unless overexpressed. Consequently, it is not likely to be abundant enough in adult tissues to functionally compete with p120. ARVCF also completely lacked the ability to induce the cell-branching phenotype associated with overexpression of p120. Expression of ARVCF/p120 chimeras confirmed previous results indicating that the branching activity of p120 maps to its Armadillo repeat domain. Surprisingly, the preferential localization of ARVCF to the nucleus required sequences in the amino-terminal end of ARVCF, suggesting that the sequences directing nuclear translocation of ARVCF are distinct from the predicted bipartite nuclear localization signal located between repeats 6 and 7. The dual localization of ARVCF to junctions and to nuclei suggests activities in different cellular compartments, as is the case for several other Armadillo repeat proteins including beta-catenin, p120 and the plakophilins.

Animals↗