Chromatin landscape and DNA repair dynamics at dysfunctional telomeres

The National Institute of General Medical Sciences awarded The Regents of The University of Colorado, doing business as University of Colorado-Denver, $429,000 on September 1, 2026, under the Biomedical Research and Research Training program (CFDA 93.859) to investigate chromatin landscape and DNA repair dynamics at dysfunctional telomeres.

The research applies a multiscale approach integrating cell and molecular biology, chromatin biology, and single-molecule imaging to understand how critically short, dysfunctional telomeres adopt altered molecular architecture marked by changes in shelterin abundance, stoichiometry, and spatial distribution that enable the microhomology-mediated end joining (MMEJ) repair pathway. The project develops in vitro systems of spontaneous telomere dysfunction in isogenic normal human fibroblasts and epithelial cells undergoing replicative aging to precisely monitor telomere dynamics as cells approach telomere crisis and DNA damage recognition and repair pathways become engaged at chromosome ends. Research addresses key questions including what chromatin landscape underlies telomere dysfunction, how changes in shelterin stoichiometry and spatial distribution establish a deprotected telomere state, how telomere-driven MMEJ is regulated and why it outcompetes classical non-homologous end joining and homologous recombination at chromosome ends, and which regulatory factors govern these processes.

Performance runs from September 1, 2026, through May 31, 2031, at the University of Colorado-Denver location in Aurora, Colorado. The award is classified as a Project Grant, an assistance type supporting investigator-initiated biomedical research under NIGMS's mission to increase understanding of biological processes and lay foundation for advances in disease diagnosis, treatment, and prevention.

Abstract

Telomeres are specialized nucleoprotein complexes that protect chromosome ends from being misidentified as DNA double-strand breaks, thereby preventing catastrophic genomic instability. This protective function relies on shelterin, a six-member multiprotein complex (TRF1, TRF2, POT1, RAP1, TIN2, TPP1) that coats telomeric DNA. Although shelterin can assemble into subcomplexes with varying compositions, how these distinct configurations prevent inappropriate DNA repair at chromosome ends remains poorly understood. In this R35 proposal, we advance a novel model of telomere end protection. We hypothesize that critically short, dysfunctional telomeres adopt an altered molecular architecture-marked by changes in shelterin abundance, stoichiometry, and spatial distribution-that enables the microhomology-mediated end joining (mmej) repair pathway. We propose that this aberrant state gives rise to a unique signature of sister chromatid fusion and complex genomic rearrangements that remain incompletely understood. To investigate this, we have developed in vitro systems of spontaneous telomere dysfunction in isogenic normal human fibroblasts and epithelial cells undergoing replicative aging, allowing US to precisely monitor telomere dynamics as cells approach telomere crisis, when DNA damage recognition and repair pathways become engaged at chromosome ends. We will employ a multiscale approach-integrating cell and molecular biology, chromatin biology, and single-molecule imaging-to address key questions in telomere biology: what chromatin landscape underlies telomere dysfunction; how changes in shelterin stoichiometry and spatial distribution across telomeric DNA establish a deprotected telomere state; how telomere-driven mmej is regulated and why IT outcompetes classical non- homologous end joining (nhej) and homologous recombination (HR) at chromosome ends; which regulatory factors govern sister-chromatid fusions; and what is the full spectrum of numerical and structural genomic aberrations stemming from these events. By leveraging our innovative tools and long-standing collaborations, we are uniquely positioned to yield transformative insights into telomere biology-ultimately illuminating new therapeutic opportunities for telomere-related disorders.