BAP1 and breast cancer: Initially BAP1 was identified in a yeast two-hybrid screen as a BRCA1-binding protein due to its interaction with the RING finger domain of this tumour suppressor (Jensen et al., 1998), and was shown to have an inhibitory effect on the growth of MCF7 breast cancer cells, indicating that BAP1 acts as a tumour suppressor gene (Jensen et al., 1998).