The Laboratory of Cell and Molecular Biology; National Institute of Diabetes and Digestive and Kidney Diseases; National Institutes of Health; Bethesda, MD USA.
Nucleus. 2013 Jul-Aug;4(4):261-6. doi: 10.4161/nucl.25341. Epub 2013 Jun 12.
In eukaryotes, chromosomes are encased by a dynamic nuclear envelope. In contrast to metazoans, where the nuclear envelope disassembles during mitosis, many fungi including budding yeast undergo "closed mitosis," where the nuclear envelope remains intact throughout the cell cycle. Consequently, during closed mitosis the nuclear envelope must expand to accommodate chromosome segregation to the two daughter cells. A recent study by Witkin et al. in budding yeast showed that if progression through mitosis is delayed, for example due to checkpoint activation, the nuclear envelope continues to expand despite the block to chromosome segregation. Moreover, this expansion occurs at a specific region of the nuclear envelope- adjacent to the nucleolus- forming an extension referred to as a "flare." These observations raise questions regarding the regulation of nuclear envelope expansion both in budding yeast and in higher eukaryotes, the mechanisms confining mitotic nuclear envelope expansion to a particular region and the possible consequences of failing to regulate nuclear envelope expansion during the cell cycle.
在真核生物中，染色体被动态的核膜所包裹。与在有丝分裂期间核膜解体的后生动物不同，许多真菌，包括芽殖酵母，经历“封闭有丝分裂”，其中核膜在整个细胞周期中保持完整。因此，在封闭有丝分裂期间，核膜必须扩张以适应染色体分离到两个子细胞中。最近 Witkin 等人在芽殖酵母中的一项研究表明，如果有丝分裂的进程被延迟，例如由于检查点的激活，那么尽管染色体分离被阻断，核膜仍会继续扩张。此外，这种扩张发生在核膜的特定区域——与核仁相邻——形成一个被称为“耀斑”的延伸。这些观察结果提出了关于核膜扩张的调控的问题，不仅在芽殖酵母中，而且在高等真核生物中，限制有丝分裂核膜扩张到特定区域的机制，以及在细胞周期中未能调控核膜扩张的可能后果。
