RESUMO
BACKGROUND: Breast cancer is increasing among young women in Tunisia. Germline mutations in the BRCA1/2 genes are associated with a high risk for breast cancer development. However, the true contribution of BRCA1/2 mutation in sporadic breast cancer is not well documented. Our aim is to identify the BRCA2 mutation spectrum in Tunisian young women with breast cancer. METHODS: Screening the BRCA2 gene was performed using DHPLC, DNA sequencing and PCR-RFLP. RESULTS: We identified, in a woman diagnosed with early onset breast cancer, and without family history, a novel in frame deletion 5456delGTAGCA in the exon 11 of the BRCA2 gene which causes a loss of two residues Ser1743-Ser1744. The absence of this deletion in the patients' parents suggests that it is a de novo variant. Furthermore, we screened 108 sporadic cases, 50 familial cases, and 60 controls for the identified del6bp using PCR-RFLP. None of them carried this deletion suggesting that this variant is not a benign polymorphism and probably rare in our population. With regards to the position of the Ser1743-1744 in the BRCT domain, sequence alignment revealed that the Ser1743 is conserved among several species, which may reflect its importance in the BRCA2 function. A modeling of the wild-type and mutated BRC5-BRC6 domain revealed that the deletion of the 2 Serine residues might affect the structure of this BRCA2 domain. CONCLUSIONS: A novel in frame deletion 5456del6bp in BRCA2 gene was identified in an early onset woman with breast cancer and without family history.
Assuntos
Neoplasias da Mama/genética , Genes BRCA2 , Deleção de Sequência , Adulto , Idade de Início , Idoso , Idoso de 80 Anos ou mais , Sequência de Aminoácidos , Proteína BRCA2/química , Proteína BRCA2/fisiologia , Neoplasias da Mama/epidemiologia , Sequência Conservada , Éxons/genética , Feminino , Testes Genéticos , Humanos , Pessoa de Meia-Idade , Modelos Moleculares , Dados de Sequência Molecular , Proteínas de Neoplasias/química , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/fisiologia , Conformação Proteica , Estrutura Terciária de Proteína , Fases de Leitura/genética , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Serina/química , Especificidade da Espécie , Tunísia/epidemiologia , Adulto JovemRESUMO
We have expressed human p53 cDNA in the yeast Saccharomyces cerevisiae and shown that the level of production and the length of the p53 protein depends on the presence of untranslated mRNA regions (UTRs). The expression of the ORF alone leads to a p53 protein of correct size (53 kDa) that accumulates to high levels, concomitantly with the presence of a small amount of a p40 protein (40 kDa). However, when either the entire 5'-UTR and a part of the 3'- or 5'-UTR alone is used, this leads to the production of small amounts of the 40 kDa truncated form only. The p40 protein corresponds to a truncated form of p53 at the C-terminal extremity since it reacts only with a monoclonal antibody recognising the N-terminal epitope. This effect on the amount and length of p53 protein had no correlation at the mRNA level, suggesting that translational control probably occurs through the 5'-UTR. We propose a model of structural interaction between this UTR and a part of the ORF mRNA for the regulation of p53 expression in this heterologous context.
Assuntos
Regiões 5' não Traduzidas/genética , Fases de Leitura Aberta/genética , Saccharomyces cerevisiae/genética , Proteína Supressora de Tumor p53/genética , Regiões 3' não Traduzidas/genética , Northern Blotting , Western Blotting , Divisão Celular/genética , DNA Complementar/genética , Regulação da Expressão Gênica , Humanos , Plasmídeos/genética , Biossíntese de Proteínas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Saccharomyces cerevisiae/crescimento & desenvolvimento , Deleção de Sequência , Transcrição Gênica , Proteína Supressora de Tumor p53/metabolismoRESUMO
The S nucleotide sequences of five hepatitis B virus strains isolated from plasma samples of Tunisian patients with chronic hepatitis B were determined; the preS2 region of three of them were sequenced. According to the comparative analysis of S peptide sequences with the reported sequences in the database bank, the five hepatitis B strains were shown to be related to the D genotypic group, subtype ayw. The nature of residues at positions 125 and 127 allowed us to distinguish between each subtype of the D group and to class all five Tunisian sequences in the 'ayw2' subtype. Moreover, two of them (1366 and 523) contained a substitution of the invariant Cys69 by Arg and Cys221 by Phe, respectively. Potential structural modifications due to the Cys-Arg change are discussed.
