Neighbor Of BRCA1 Gene 1 (NBR1)

NBR1 was originally identified as an ovarian tumor antigen monitored in ovarian cancer. The encoded protein contains a B-box/coiled coil motif, which is present in many genes with transformation potential, but the function of this protein is unknown. This gene is located on a region of chromosome 17q21.1 that is in close proximity to tumor suppressor gene BRCA1. Three alternatively spliced variants encoding the same protein have been identified for this gene. NBR1 targets the ubiquitin-associated p62/SQSTM1 to sarcomeres, and p62 in turn interacts with MURF2, a muscle-specific RING-B-box E3 ligase and ligand of the transactivation domain of the serum response transcription factor (SRF). Nuclear translocation of MURF2 was induced by mechanical inactivity and caused reduction of nuclear SRF and repression of transcription.