Transcription‐independent role of Bach1 in mitosis through a nuclear exporter Crm1‐dependent mechanism

The transcriptional repressor Bach1 mediates various stress responses. Despite its role in transcription, Bach1 is predominantly exported to the cytoplasm in a Crm1‐dependent manner, but the functional role of its cytoplasmic retention is still unclear. We found that Bach1 was also excluded from mitotic chromatin by a C‐terminal cytoplasmic localization sequence dependent and leptomycin B sensitive process. Bach1 depletion resulted in disordered mitotic chromosome alignment, which was rescued by Bach1 mutants lacking the BTB or DNA binding domains, suggesting its transcription‐independent mechanism. We thus revealed a novel role of Bach1 in the regulation of mitotic chromosome dynamics.