Homologous recombination (HR) are one of double-strand break (DSB) repair pathways. BRCA1 and BRCA2, associated with the RAD51 protein, accumulates in DNA damage foci after signaling H2AX, a DNA damage marker that accumulates in lesion foci, associated to ATM/ATR pathway, leading to DNA repair. Topoisomerase III beta (TopoIII beta) removes HR intermediates before the segregation of chromosomes, preventing damage to the structure of the cellular DNA. Bmi -1 is a Polycomb group protein which is able to induce telomerase activity, enabling the immortalization of epithelial cells. Immortalized cells shown more susceptible to double-strand breaks. The role of proteins involved in HR, in breast carcinomas positive for BMI-1, remains to be investigated. This way, our objective is to evaluate the relationship between BMI-1 and regulatory proteins of homologous recombination. For this, we will cultivate MCF-7 cells, which constitutively express the BMI-1. From this culture, two groups will be assembled, the BMI-1 positive and silenced BMI-1, both in triplicate. For the analysis of gene and protein expression and immunolocalization will be used, respectively, qRT-PCR assays, Western blot and indirect immunofluorescence in order to analyze the expression of genes and proteins associated with HR (BRCA1 and 2, ATM, ATR, p53, TopoIII beta, RAD51 and H2AX) in the presence and absence of BMI-1. For functional characterization of cells BMI-1 positive and negative, we will carry out invasion assays in Matrigel matrix, apoptosis assays by immunofluorescence and cell proliferation assays.
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