The Molecular Mechanism Of BAP1 Mutation-induced Chromosomal Instability In Renal Cell Carcinomas

Objectives:: BAP1 is a deubiquitnase that controls proteins abundance and catalyzes ubiquitin hydrolysis.Several exome sequencing studies showed that BAP1 was inactivated in 15% of clear cell renal cell carcinoma(cc RCC).Moreover,BAP1 mutation was associated with aggressive features(high tumor grade)and poor diagnosis.However,the functional relationship between BAP1 mutation and cc RCC tumorigenesis remains unknown.In this study,we will investigate the highly mutated BAP1's role in regulation of chromosomal instability.Methods: Yeast two-hybrid screening assay was used to identify the interactive protein of BAP1,then tandem affinity purification to analyze the recombinant BAP1 protein complex in vivo;Western blot,immunofluorescence and Site-directed mutagenesis were used to verify the interaction and ubiquitination between BAP1 and MCRS1.At last,Immunohistochemistry was performed on 31 pairs of cc RCC specimens to investigate the expression of BAP1 and MCRS1.Results: We identified centrosome proteins MCRS1 as a bona fide substrate for BAP1.BAP1 binds to MCRS1 and stabilizes MCRS1 by de-ubiquitination.BAP1 contributes to chromosome stability partially via MCRS1.A positive correlation was identified between BAP1 and MCRS1 expression in cc RCC tissues.Both BAP1 loss and MCRS1 downregulation in cc RCC were associated with adverse clinicopathological features.Conclusion: This study revealed a novel mechanism for BAP1 involved in MCRS1 stability regulation,and provided insight in understanding the relationship between BAP1 mutations and chromosome instability in cc RCC.