PBRM1 and nonpapillary renal cell carcinoma: Exome sequencing has revealed that 40% of ccRCC tumors also harbor mutations in the polybromo-1 (PBRM1) gene that codes for the BAF180 protein (we will use the term of BAF180 for the gene and the protein, for simplicity), an accessory component of the PBAF complex, one type of SWI/SNF chromatin remodeling complex.7, 8, 9, 10, 11 SWI/SNF chromatin remodeling complexes regulate gene transcription through nucleosome disruption and reconstruction in an ATP-dependent manner.