The EHMT2-MBLAC2 axis suppresses ribosomal DNA transcription in response to nucleolar DNA damage

  • Cell Death Dis. 2026 Mar 18;17(1):320. doi: 10.1038/s41419-026-08616-1.
Chenyue Wang  #  1 ,  Qiutian Lu  #  1 ,  Lianbao Cao  2 ,  Simeng Zeng  1 ,  Zihan Gao  1 ,  Yinglong Yang  1 ,  Xiaowen Liu  1 ,  Shanshan Gao  3  4 ,  Chao Dong  5
Affiliations
  • 1. Department of Occupational and Environmental Health, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, China.
  • 2. Department of Gynecologic Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China.
  • 3. Futaste Pharmaceutical Co. Ltd., Dezhou, Shandong, China. [email protected].
  • 4. Department of Gastroenterology, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, Shandong, China. [email protected].
  • 5. Department of Occupational and Environmental Health, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, China. [email protected].
  • # Contributed equally.
PMID: 41851073 DOI: 10.1038/s41419-026-08616-1
Abstract

The induction of DNA double-strand breaks (DSBs) within actively transcribed ribosomal DNA (rDNA) arrays triggers transcriptional suppression and drives nucleolar reorganization, including the formation of nucleolar caps that facilitate the engagement of DSBs with canonical DSB signaling and repair proteins. Although these nucleolar responses are critical for rDNA stability, the components that orchestrate these responses remain unclear. In this study, we identified euchromatic histone-lysine N-methyltransferase 2 (EHMT2) as a novel regulator that is essential for rDNA DSB-induced transcriptional suppression, while functioning independently of ATM-mediated nucleolar responses. We found that EHMT2 is required for the repair of rDNA DSBs and the maintenance of rDNA stability, and its deficiency can result in cellular hypersensitivity to rDNA DSBs. Global proteomic analysis revealed that EHMT2 interacts with MBLAC2 to repress rDNA transcription upon rDNA DSBs. The depletion of EHMT2 or MBLAC2 sensitized colorectal Cancer cells to ribosomal stress. Furthermore, we uncovered that EHMT2 promotes colorectal tumorigenesis, revealing a novel mechanistic link between rDNA transcriptional regulation and tumor promotion. Together, our findings established the EHMT2-MBLAC2 axis as a pivotal regulator of mammalian rDNA DSB-induced transcriptional silencing that coordinates rDNA DSB repair and the maintenance of rDNA integrity during nucleolar damage.

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