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.

► We revealed that Bach1 has a novel function beyond transcriptional regulation.
► Bach1 functions to maintain mitotic chromosome alignment.
► The exclusion of Bach1 from mitotic chromosome is required for the activity.
► Crm1-mediated regulation is involved in this process.
► DNA binding activity of Bach1 is dispensable for the activity.