Expression of human BRCA1¦¤17-19 alternative splicing variant with a truncated BRCT domain in MCF-7 cells results in impaired assembly of DNA repair complexes and aberrant DNA damage response

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• 作者：Jan Sevcik^a ; ^e ; ^{jsevc@lf1.cuni.cz} ; Martin Falk^b ; Libor Macurek^c ; ^d ; Petra Kleiblova^a ; Filip Lhota^a ; Jan Hojny^a ; Lenka Stefancikova^b ; Marketa Janatova^a ; Jiri Bartek^c ; ^f ; ^g ; Jana Stribrna^a ; Zdenek Hodny^c ; Lucie Jezkova^b ; ^h ; Petr Pohlreich^a ; Zdenek Kleibl^a ; ^{zdekleje@lf1.cuni.cz}
• 关键词：AS ; alternative splicing ; ASV ; alternative splicing variant ; B2M ; ¦Â-2-microglobulin ; BARD1 ; BRCA1-associated RING domain 1 ; BC ; breast cancer ; BRCA1/2 ; breast cancer-associated gene 1/2 ; BRCT ; BRCA1 C-terminal domain ; BRCC36 ; BRCA1/BRCA2-containing compl
• 刊名：Cellular Signalling
• 出版年：2013
• 出版时间：May, 2013
• 年：2013
• 卷：25
• 期：5
• 页码：1186-1193
• 全文大小：974 K

文摘

Alternative pre-mRNA splicing is a fundamental post-transcriptional regulatory mechanism. Cancer-specific misregulation of the splicing process may lead to formation of irregular alternative splicing variants (ASVs) with a potentially negative impact on cellular homeostasis. Alternative splicing of BRCA1 pre-mRNA can give rise to BRCA1 protein isoforms that possess dramatically altered biological activities compared with full-length wild-type BRCA1. During the screening of high-risk breast cancer (BC) families we ascertained numerous BRCA1 ASVs, however, their clinical significance for BC development is largely unknown. In this study, we examined the influence of the BRCA1¦¤17-19 ASV, which lacks a portion of the BRCT domain, on DNA repair capacity using human MCF-7 BC cell clones with stably modified BRCA1 expression. Our results show that overexpression of BRCA1¦¤17-19 impairs homologous recombination repair (sensitizes cells to mitomycin C), delays repair of ionizing radiation-induced DNA damage and dynamics of the ionizing radiation-induced foci (IRIF) formation, and undermines also the non-homologous end joining repair (NHEJ) activity. Mechanistically, BRCA1¦¤17-19 cannot interact with the partner proteins Abraxas and CtIP, thus preventing interactions known to be critical for processing of DNA lesions. We propose that the observed inability of BRCA1¦¤17-19 to functionally replace wtBRCA1 in repair of DNA double-strand breaks (DDSB) reflects impaired capacity to form the BRCA1-A and -C repair complexes. Our findings indicate that expression of BRCA1¦¤17-19 may negatively influence genome stability by reducing the DDSB repair velocity, thereby contributing to enhanced probability of cancer development in the affected families.