Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA; Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA; Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
J Biol Chem. 2023 Jul;299(7):104834. doi: 10.1016/j.jbc.2023.104834. Epub 2023 May 17.
Chromatin organization is highly dynamic and modulates DNA replication, transcription, and chromosome segregation. Condensin is essential for chromosome assembly during mitosis and meiosis, as well as maintenance of chromosome structure during interphase. While it is well established that sustained condensin expression is necessary to ensure chromosome stability, the mechanisms that control its expression are not yet known. Herein, we report that disruption of cyclin-dependent kinase 7 (CDK7), the core catalytic subunit of CDK-activating kinase, leads to reduced transcription of several condensin subunits, including structural maintenance of chromosomes 2 (SMC2). Live and static microscopy revealed that inhibiting CDK7 signaling prolongs mitosis and induces chromatin bridge formation, DNA double-strand breaks, and abnormal nuclear features, all of which are indicative of mitotic catastrophe and chromosome instability. Affirming the importance of condensin regulation by CDK7, genetic suppression of the expression of SMC2, a core subunit of this complex, phenocopies CDK7 inhibition. Moreover, analysis of genome-wide chromatin conformation using Hi-C revealed that sustained activity of CDK7 is necessary to maintain chromatin sublooping, a function that is ascribed to condensin. Notably, the regulation of condensin subunit gene expression is independent of superenhancers. Together, these studies reveal a new role for CDK7 in sustaining chromatin configuration by ensuring the expression of condensin genes, including SMC2.
染色质组织高度动态，调节着 DNA 复制、转录和染色体分离。在有丝分裂和减数分裂过程中，凝聚素对于染色体的组装是必不可少的，同时在间期也维持着染色体的结构。虽然已经证实持续的凝聚素表达对于确保染色体稳定性是必需的，但控制其表达的机制尚不清楚。在此，我们报告细胞周期蛋白依赖性激酶 7（CDK7）的破坏，即 CDK-激活激酶的核心催化亚基，导致几个凝聚素亚基的转录减少，包括染色体维持结构 2（SMC2）。活细胞和静态显微镜观察显示，抑制 CDK7 信号会延长有丝分裂并诱导染色质桥形成、DNA 双链断裂和异常核特征，所有这些都表明有丝分裂灾难和染色体不稳定。证实了 CDK7 对凝聚素调节的重要性，该复合物的核心亚基 SMC2 的表达被遗传抑制，表现出与 CDK7 抑制相似的表型。此外，使用 Hi-C 对全基因组染色质构象的分析表明，CDK7 的持续活性对于维持染色质亚环，这一功能归因于凝聚素，是必需的。值得注意的是，凝聚素亚基基因表达的调控独立于超级增强子。总的来说，这些研究揭示了 CDK7 通过确保凝聚素基因（包括 SMC2）的表达来维持染色质构象的新作用。
