Effects of the Missense Mutations in Canine BRCA2 on BRC Repeat 3 Functions and Comparative Analyses between Canine and Human BRC Repeat 3

Yasunaga Yoshikawa,Kiyotaka Watanabe,Satomi Iwai,Koichi Orino,Kazuhiko Ochiai,Masami Morimatsu,Takahiro Taoda,Yu Suzuki,Seishiro Chikazawa,Seiichi Wada,Michel M Ouellette

doi:10.1371/journal.pone.0045833

Yasunaga Yoshikawa, Kiyotaka Watanabe + Show 9 more

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https://doi.org/10.1371/journal.pone.0045833

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Abstract

Mammary tumors are the most common tumor type in both human and canine females. Mutations in the breast cancer susceptibility gene, BRCA2, have been found in most cases of inherited human breast cancer. Similarly, the canine BRCA2 gene locus has been associated with mammary tumors in female dogs. However, deleterious mutations in canine BRCA2 have not been reported, thus far. The BRCA2 protein is involved in homologous recombination repair via its interaction with RAD51 recombinase, an interaction mediated by 8 BRC repeats. These repeats are 26-amino acid, conserved motifs in mammalian BRCA2. Previous structural analyses of cancer-associated mutations affecting the BRC repeats have shown that the weakening of RAD51's affinity for even 1 repeat is sufficient to increase breast cancer susceptibility. In this study, we focused on 2 previously reported canine BRCA2 mutations (T1425P and K1435R) in BRC repeat 3 (BRC3), derived from mammary tumor samples. These mutations affected the interaction of canine BRC3 with RAD51, and were considered deleterious. Two BRC3 mutations (K1440R and K1440E), reported in human breast cancer patients, occur at amino acids corresponding to those of the K1435R mutation in dogs. These mutations affected the interaction of canine BRC3 with RAD51, and may also be considered deleterious. The two BRC3 mutations and a substitution (T1430P), corresponding to T1425P in canine BRCA2, were examined for their effects on human BRC3 function and the results were compared between species. The corresponding mutations and the substitution showed similar results in both human and canine BRC3. Therefore, canine BRCA2 may be a good model for studying human breast cancer caused by BRCA2 mutations.

Highlights

Mammary tumors are the most common tumor type in both human and canine females, and the molecular biological similarities between the tumors in both species are well conserved [1,2,3,4]
The level of interaction between cBRC3 and human RAD51 (hRAD51) was shown to be stronger than that between human BRC3 (hBRC3) and hRAD51 (Figure 1 B). This assay showed that the level of interaction between hBRC3, canine BRC4 (cBRC4) or hBRC4, and canine RAD51 (cRAD51) or hRAD51 was different, depending on the animal species of RAD51 (Supporting information Figure S1)
The effect of 2 missense mutations located in cBRC3, an amino acid sequence that is important for mediating the interaction between BRCA2 and RAD51 [13,19], was examined for their effect on the functioning of cBRC3

Summary

Introduction

Mammary tumors are the most common tumor type in both human and canine females, and the molecular biological similarities between the tumors in both species are well conserved [1,2,3,4]. The breast cancer susceptibility gene, BRCA2, has been identified as a tumor-suppressor gene. Germ-line mutations in BRCA2 predispose women to a high risk of breast cancer. Genetic analyses, including detection of deleterious mutations, to identify carriers of BRCA2 mutation is strongly advocated as the lifetime risk of breast cancer is high (81–88%) for women carrying this mutation [5,6]. All mammalian BRCA2 proteins contain 8 BRC repeats, clustered on exon 11, and located in the central portion of the protein; these repeats show significant sequence conservation [8]. These structural characteristics indicate the importance of the BRC domain

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