Impaired Effects of a FANCC Splicing Isoform in FANC-BRCA DNA Repair Pathway

Simon Bélanger ,Beauparlant Cj ,St-Laurent Pedneault C ,G Ouellette ,Y Labrie ,Karine V Plourde ,Francois Bouffard ,Francine Durocher

doi:10.4172/2157-7412.1000144

Abstract

The integrity of the FANC gene family is essential for the proper reparation of DNA damages. Recently, different FANCC splice variants were identified. We characterized sequence variations and studied the impact of the alternative splicing event FANCCâ7 on DNA repair. The FANCCâ7 transcript is present in all breast cancer lines analyzed. Genomic and complementary DNA sequencing of non-BRCA1/2 individuals was performed to identify sequence variants and alternative transcripts of the FANCC gene. Ribosomal fractions allowed confirming the translation of FANCCâ7 into a functional protein. The variant protein seems to be secluded in the cytoplasm in transfected HEK293T cells following MMC treatments contrary to the FANCC protein that migrates to the nucleus. Performing localization studies, we observed evidences of colocalization of FANCC and FANCCâ7 with BRCA1 in centrosomes of cells. We demonstrated that FANCC deficient cells infected with FANCCâ7 cDNA show a blocking in G2/M in the presence of MMC. Finally, FANCCâ7 is unable to allow the monoubiquitination of FANCD2. This study unravels the incapability of the FANCCâ7 splicing event to permit the reparation of interstrand crosslinks induced by MMC. This work unravels a novel layer of complexity to the understanding of the fascinating FANC-BRCA DNA repair pathway.

Highlights

Pathogenic mutations in BRCA1, BRCA2/FANCD1, TP53, ATM, CHEK2, BRIP1/FANCJ, PALB2/FANCN and RAD51C/FANCO have been associated with an increased breast cancer risk and, together, are found in less than 25% of breast cancer families showing a clear pattern of inheritance [1,2,3,4,5,6,7]
The previous identification of BRCA2/FANCD1, PALB2/FANCN, BRIP1/FANCJ and FANCO/RAD51C as breast cancer susceptibility genes further strengthens the implication of Fanconi anemia (FA) genes in breast cancer susceptibility [21,30,32,34]
As the French Canadian (FC) population is considered a founder population, this allows to increase the likelihood of potentially identifying genetic variants associated with breast cancer [35] in nonBRCA1/2 high-risk families

Summary

Introduction

Pathogenic mutations in BRCA1, BRCA2/FANCD1, TP53, ATM, CHEK2, BRIP1/FANCJ, PALB2/FANCN and RAD51C/FANCO have been associated with an increased breast cancer risk and, together, are found in less than 25% of breast cancer families showing a clear pattern of inheritance [1,2,3,4,5,6,7]. A recent study conducted with 944 family members being part of the International Fanconi Anemia Registry revealed an increased risk of breast cancer among grandmothers carriers of FANCC mutations [24]. In response to interstrand crosslinking (ICL) damage, this FA/BRCA network activates and coordinates a complex DNA repair mechanism involving homologous recombination (HR), nucleotide excision repair and translesion DNA synthesis [20]. FANCC (localized in both the cytoplasm and nucleus) is implicated in several other cytoplasmic functions such as JAK/STAT and apoptotic signaling [26,27,28,29]

Methods

Results

Conclusion