Ingham Andreas, de Vega Ignacio Alonso, Morlot Louise, Gittens William, Hendriks Ivo A, Kakulidis Ellen S, Freire Raimundo, Davey Norman E, Duxin Julien P, Lund Nielsen Michael, Mailand Niels
Protein Signaling Program, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, 2200 Copenhagen, Denmark; Center for Chromosome Stability, Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen, Denmark.
Protein Signaling Program, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, 2200 Copenhagen, Denmark.
Mol Cell. 2025 Jul 3;85(13):2487-2502.e12. doi: 10.1016/j.molcel.2025.04.006. Epub 2025 Jun 13.
Topoisomerase II (TOP2) inhibitors (TOP2i) are mainstay chemotherapeutic agents that undermine genome integrity by stabilizing TOP2-DNA complexes accompanied by DNA damage formation. Here, we reveal the uncharacterized protein CRAMP1 and H1 linker histones as key effectors of TOP2i tolerance in human cells. We demonstrate that CRAMP1 defines a dedicated histone H1 biogenesis factor stimulating transcription of both replicative and non-replicative H1 genes, driven by its concurrent targeting to histone gene loci and H1-specific promoter motifs. CRAMP1 promotes TOP2i tolerance by maintaining H1 supply, involving a novel mechanism uncoupled from TOP2i-induced DNA damage whereby reducing the H1 pool triggers unscheduled TOP2 substrate formation in low-accessibility chromatin states. This amplifies total demand for TOP2 activity, lowering the threshold for TOP2i-mediated exhaustion of TOP2. Our discoveries elucidate the mechanistic basis of histone H1 biogenesis in human cells, opening opportunities for selectively manipulating linker but not core histone supply and targeting cancer-associated H1 deficiency.
拓扑异构酶II（TOP2）抑制剂（TOP2i）是主要的化疗药物，其通过稳定TOP2-DNA复合物并伴随DNA损伤形成来破坏基因组完整性。在此，我们揭示了未被表征的蛋白质CRAMP1和H1连接组蛋白是人类细胞中TOP2i耐受性的关键效应因子。我们证明，CRAMP1定义了一种专门的组蛋白H1生物合成因子，它通过同时靶向组蛋白基因位点和H1特异性启动子基序，刺激复制型和非复制型H1基因的转录。CRAMP1通过维持H1供应来促进TOP2i耐受性，这涉及一种与TOP2i诱导的DNA损伤无关的新机制，即减少H1库会在低可及性染色质状态下引发非计划的TOP2底物形成。这增加了对TOP2活性的总需求，降低了TOP2i介导的TOP2耗竭阈值。我们的发现阐明了人类细胞中组蛋白H1生物合成的机制基础，为选择性操纵连接组蛋白而非核心组蛋白供应以及靶向癌症相关的H1缺陷提供了机会。
