Localization of BRCA1 protein at the cellular level

Based on its amino acid sequence and theexistence of three nuclear localization signal(NLS)3 regions, BRCA1 is likely to be a cellcycle-dependent nuclear protein, regulated bycyclindependent kinases (cdk) and associated with nuclear proteins suchas Rad51 and BARD1, involved in transcription regulationand participating in DNA replication checkpoints.However, many authors have also described a cytoplasmic expression pattern. Moreover, BRCA1 was presentnot only in a dot like pattern in the nucleus but alsoassociated with a channel-like system of cytoplasm andendoplasmic reticulum invaginating into the nucleus. BRCA1 expression patterns can also beinfluenced by alternative splice variants and by cellcycledependent expression level and localization.Further ultrastructural and confocal studies using C-terminal antibodies, that do not react withC-terminal truncated form of BRCA1 should shed new lightupon the exact localization of BRCA1.