Transcription factors play a key role in maintaining cell identity. One mechanism of such cell memory after multiple rounds of cell division cycles is through persistent mitotic chromosome binding, although how individual transcription factors achieve mitotic chromosome retention is not completely understood. Here we show that PAX6, a lineage-determining transcription factor, coats mitotic chromosomes. Using deletion and point mutants associated with human ocular diseases in live-cell imaging analysis, we identified two regions, MCR-D1 and MCR-D2, that were responsible for mitotic chromosome retention of PAX6. We also identified three nuclear localization signals (NLSs) that contributed to mitotic chromosome retention independent of their nuclear import functions. Full mitotic chromosome retention required the presence of DNA-binding domains as well as NLSs within MCR-Ds. Furthermore, disease-associated mutations and NLS mutations changed the distribution of intrinsically disordered regions (IDRs) in PAX6. Our findings not only identify PAX6 as a novel mitotic chromosome retention factor but also demonstrate that the mechanism of mitotic chromosome retention involves sequence-specific DNA binding, NLSs, and molecular conformation determined by IDRs. These findings link mitotic chromosome retention with PAX6-related pathogenesis and imply similar mechanisms for other lineage-determining factors in the PAX family.

转录因子在维持细胞身份中起关键作用。在多轮细胞分裂周期后，这种细胞记忆的一种机制是通过持久的有丝分裂染色体结合，尽管个体转录因子如何实现有丝分裂染色体保留尚不完全清楚。这里我们展示了 PAX6，一种谱系决定转录因子，覆盖有丝分裂染色体。在活细胞成像分析中使用与人类眼部疾病相关的缺失和点突变，我们确定了两个区域，MCR-D1 和 MCR-D2，它们负责 PAX6 的有丝分裂染色体保留。我们还确定了三个核定位信号 (NLS)，它们有助于独立于核输入功能的有丝分裂染色体保留。完整的有丝分裂染色体保留需要在 MCR-D 中存在 DNA 结合域和 NLS。此外，疾病相关突变和 NLS 突变改变了 PAX6 中固有无序区域 (IDR) 的分布。DNA 结合、NLS 和由 IDR 确定的分子构象。这些发现将有丝分裂染色体保留与 PAX6 相关发病机制联系起来，并暗示 PAX 家族中其他谱系决定因素的类似机制。