TRIM24 directs replicative stress responses to maintain ALT telomeres via chromatin signaling

Daein Kim; Ragini Bhargava; Shih-Chun Wang; Wei-Che Tseng; Doohyung Lee; Riya Patel; Sungtaek Oh; Ray W Bowman 2nd; Baylee A Smith; Minkyu Kim; Chan Hyun Na; Roderick J O'Sullivan; Kyle M Miller

doi:10.1016/j.molcel.2025.06.009

TRIM24 directs replicative stress responses to maintain ALT telomeres via chromatin signaling

Mol Cell. 2025 Jun 27:S1097-2765(25)00509-X. doi: 10.1016/j.molcel.2025.06.009. Online ahead of print.

Authors

Affiliations

¹ Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA.
² Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA 15232, USA.
³ Department of Neurology, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
⁴ Department of Biochemistry & Structural Biology, Long School of Medicine, UT Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
⁵ Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA 15232, USA. Electronic address: rjo@pitt.edu.
⁶ Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA; Livestrong Cancer Institutes, Dell Medical School, The University of Texas at Austin, Austin, TX 78712, USA. Electronic address: kyle.m.miller@emory.edu.

PMID: 40614724
DOI: 10.1016/j.molcel.2025.06.009

Abstract

An inability to replicate the genome can cause replication stress and genome instability. Here, we develop biotinylation of lac operator (LacO) array replication stress protein network identification (BLOCK-ID) in human cancer cells, a proteomic method to identify and visualize proteins at stressed replication forks. This approach identified mediators of the replication stress response, including the chromatin acetylation reader protein tripartite motif containing 24 (TRIM24). We uncovered a crucial role for TRIM24 in coordinating alternative lengthening of telomeres (ALT), a replication stress-directed telomere extension mechanism. Our data reveal that TRIM24 is recruited to telomeres via a p300/CREB binding protein (CBP)-dependent acetylation chromatin signaling cascade to organize the assembly of ALT-associated promyelocytic leukemia (PML) bodies (APBs) and promote de novo telomere DNA synthesis. Tethering of TRIM24 at telomeres was sufficient to stimulate de novo telomere DNA synthesis in a small ubiquitin-like modifier (SUMO)-dependent but p300/CBP- and PML-independent manner. Collectively, these findings uncover an indispensable epigenetic signaling pathway involving TRIM24 and p300/CBP that mediates ALT-telomere maintenance.

Keywords: ALT; BLOCK-ID; PML; SUMOylation; TRIM24; acetylation; chromatin; p300; replication stress; telomeres.