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Alan Ashworth

Publications and source records attributed to Alan Ashworth.

61 records · Page 4Linked to original sources
PubMed2002

MAP kinase phosphatases.

Mitogen-activated protein MAP kinases are key signal-transducing enzymes that are activated by a wide range of extracellular stimuli. They are responsible for the induction of a number of cellular responses, such as changes in gene expression, proliferation, differentiation, cell cycle arrest and apoptosis. Although regulation of MAP kinases by a phosphorylation cascade has long been recognized as significant, their inactivation through the action of specific phosphatases has been less studied. An emerging family of structurally distinct dual-specificity serine, threonine and tyrosine phosphatases that act on MAP kinases consists of ten members in mammals, and members have been found in animals, plants and yeast. Three subgroups have been identified that differ in exon structure, sequence and substrate specificity.

Amino Acid Sequence↗
PubMed2002

Differential effects of stress stimuli on a JNK-inactivating phosphatase.

Stress signals elicit a wide variety of cellular responses, many of which converge on the phosphorylation of JNK and p38 kinases, the activation of which has been well-characterized. How these kinases are switched off by dephosphorylation is not well understood. Here we describe how diverse cellular stresses affect differently the stability and activity of a JNK-inactivating dual-specificity threonine-tyrosine phosphatase M3/6. Both anisomycin and arsenite activate the JNK pathway and, in addition, inactivate the M3/6 phosphatase. However, while anisomycin treatment of cells leads to M3/6 protein degradation, arsenite appears to inactivate M3/6 directly. These results might have implications for the mechanism of tumour promotion by arsenic.

Acetylcysteine↗
PubMed2002

Structural analysis of the chicken BRCA2 gene facilitates identification of functional domains and disease causing mutations.

Carriers of mutations in the BRCA2 gene have a high risk of developing breast and other cancers. The BRCA2 gene, which is located on human chromosome 13, encodes a very large protein of only poorly understood function. To define regions of sequence conservation and highlight potentially functionally important domains, we have cloned and characterized the chicken BRCA2 gene, the first non-mammalian BRCA2 gene to be described. The gene is organized similarly to the human BRCA2 gene, but is more compact and is localized to the subtelomeric region of chicken chromosome 1q, within a region that contains other genes from human chromosome 13. The chicken BRCA2 gene encodes a protein of 3399 amino acids, which is poorly conserved with mammalian BRCA2 proteins, having only 37% amino acid identity overall with human BRCA2. However, certain domains are much more highly conserved, indicating functional significance. We describe genes with some of these conserved domains in organisms as diverse as intracellular parasites, mosquitoes and plants. The evolutionarily divergent chicken BRCA2 sequence may also be useful in assigning the large number of sequence variants that have been described in the human BRCA2 gene which are of unknown significance in disease causation.

Amino Acid Sequence↗
PubMed2002

Disruption of Brca2 increases the spontaneous mutation rate in vivo: synergism with ionizing radiation.

The breast cancer predisposition gene BRCA2 encodes a protein involved in the repair of DNA double-strand breaks, which arise spontaneously and following exposure to ionizing radiation (IR). To develop a mouse model that examines the effect of BRCA2 mutation and IR exposure on in vivo somatic mutation acquisition, we crossed mice with targeted disruption of Brca2 with a LacZ transgenic mutation reporter strain. Loss of both wild-type Brca2 alleles caused a 2.3-fold increase, equivalent to an extra 100 mutations per cell, in the in vivo acquisition of spontaneous somatic mutation by 2 weeks gestation. IR (4 Gy) had a disproportionate effect on animals homozygous for Brca2 disruption, inducing 3.4-fold more mutations compared with wild-type animals. These data provide the first evidence that loss of Brca2 increases in vivo somatic mutation acquisition and synergizes with IR exposure, with potential attendant implications for mammographic screening and therapeutic IR in mutation carriers.

Animals↗
PubMed2002

The relationship between the roles of BRCA genes in DNA repair and cancer predisposition.

The proteins encoded by the breast-cancer-susceptibility genes, BRCA1 and BRCA2, have recently been implicated in DNA-repair processes, thereby improving our understanding of how the loss of these genes contributes to cancer initiation and progression. It appears that the role of BRCA1 in DNA repair, which could involve the integration of several pathways, is broader than that of BRCA2. BRCA1 functions in the signalling of DNA damage and its repair by homologous recombination, nucleotide-excision repair and possibly non-homologous end-joining. BRCA2 has a more specific role in DNA repair, regulating the activity of RAD51, which is required for homologous recombination. An improved understanding of the interactions of BRCA1 and BRCA2 with other proteins in large macromolecular complexes is helping to reveal their exact role in DNA repair.

BRCA1 Protein↗
PubMedDate not supplied

Interaction between CHEK2*1100delC and other low-penetrance breast-cancer susceptibility genes: a familial study.

BACKGROUND: The allele CHEK2*1100delC doubles the risk of breast cancer in unselected women, but could confer a greater risk in women with a family history of the disease, particularly of bilateral breast cancer. Our aim was to measure the risk of breast cancer in relatives of women with bilateral breast cancer who were carriers of this allele. METHODS: A population-based series of 469 bilateral breast cancer cases ascertained through English cancer registries were genotyped for CHEK2*1100delC. Standardised incidence ratios (SIRs) and cumulative risks were calculated for breast cancer, prostate cancer, and all other cancers in the first-degree relatives of carriers and non-carriers. FINDINGS: The relatives of bilateral cases who were wild-type for CHEK2 had three times the population risk of female breast cancer (145 cases: SIR 3.48 (95% CI 2.96-4.09), twice the risk of prostate cancer (34 cases: SIR 2.41, 1.67-3.36) and a large excess of male breast cancer (five cases: SIR 15.06, 4.92-35.36). Relatives of those who were carriers of CHEK2*1100delC had a substantially higher risk of breast cancer (eight cases: SIR 12.11, 5.23-23.88) and possibly prostate cancer (two cases: SIR 9.87, 1.20-35.67). INTERPRETATION: These data suggest a multiplicative interaction between CHEK2*1100delC and other unknown susceptibility genes. In women with a family history of bilateral disease, CHEK2*1100delC confers a high lifetime risk and might be useful for predictive testing. Bilateral breast cancer cases and their families are likely to provide an efficient basis for identification of additional low-penetrance breast-cancer genes.

Adult↗