BARD1 splice variants display mislocalization in breast cancer cells and can alter the apoptotic response to cisplatin

Cancer Lett. 2016 Oct 10;381(1):149-55. doi: 10.1016/j.canlet.2016.07.034. Epub 2016 Jul 28.


We previously showed that BARD1 is a shuttling protein with pro-apoptotic activity in MCF-7 breast cancer cells. BARD1 is expressed as splice variant isoforms in breast cancer. Here we characterized YFP-tagged BARD1 splice variants (beta, omega, phi, ΔRIN, epsilon) for subcellular localization and apoptotic efficacy. We found that loss of nuclear localization (NLS) or export (NES) sequences influenced cellular distribution. The beta and omega variants (+NLS/-NES) shifted exclusively to the nucleus. In contrast, BARD1-epsilon (-NLS/+NES) was mostly cytoplasmic. Variants that lacked both NLS and NES were evenly distributed. Interestingly, the more nuclear isoforms (omega and beta) were least apoptotic in MCF-7 cells as measured by FACS. The cytoplasmic localization of BARD1 isoforms correlated with increased apoptosis. This relationship held in cells exposed to low dose (5 µM) of cisplatin. At 20 µM cisplatin, the main observation was a protective effect by the omega isoform. Similar analyses of HCC1937 cells revealed less pronounced changes but a significant protective influence by BARD1-epsilon. Thus BARD1 variants differ in localization and apoptotic ability, and their expression profile may aid prediction of drug efficacy in breast cancer.

Keywords: Apoptosis; BARD1; Breast cancer; Cisplatin; Nuclear localization; Splice variants.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus
  • Alternative Splicing
  • Antineoplastic Agents / pharmacology*
  • Apoptosis / drug effects*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / enzymology
  • Breast Neoplasms / genetics
  • Breast Neoplasms / pathology
  • Cisplatin / pharmacology*
  • Cytoplasm / enzymology
  • Dose-Response Relationship, Drug
  • Drug Resistance, Neoplasm
  • Female
  • Humans
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • MCF-7 Cells
  • Protein Isoforms
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction / drug effects
  • Transfection
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism*
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*


  • Antineoplastic Agents
  • Bacterial Proteins
  • Luminescent Proteins
  • Protein Isoforms
  • Recombinant Fusion Proteins
  • Tumor Suppressor Proteins
  • yellow fluorescent protein, Bacteria
  • BARD1 protein, human
  • Ubiquitin-Protein Ligases
  • Cisplatin