Hutchinson Gilford progeria syndrome (HGPS) is a devastating accelerated aging disease caused by LMNA gene mutation. The truncated lamin A protein produced “progerin” has a dominant toxic effect in cells, causing disruption of nuclear architecture and chromatin structure, genomic instability, gene expression changes, oxidative stress, and premature senescence. It was previously shown that progerin‐induced genomic instability involves replication stress (RS), characterized by replication fork stalling and nuclease‐mediated degradation of stalled forks. RS is accompanied by activation of cGAS/STING cytosolic DNA sensing pathway and STAT1‐regulated interferon (IFN)‐like response. It is also found that calcitriol, the active hormonal form of vitamin D, rescues RS and represses the cGAS/STING/IFN cascade. Here, the mechanisms underlying RS in progerin‐expressing cells and the rescue by calcitriol are explored. It is found that progerin elicits a marked downregulation of RAD51, concomitant with increased levels of phosphorylated‐RPA, a marker of RS. Interestingly, calcitriol prevents RS and activation of the cGAS/STING/IFN response in part through maintenance of RAD51 levels in progerin‐expressing cells. Thus, loss of RAD51 is one of the consequences of progerin expression that can contribute to RS and activation of the IFN response. Stabilization of RAD51 helps explain the beneficial effects of calcitriol in these processes.

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Hutchinson-Gilford progeria syndrome (HGPS), a devastating premature aging disease caused by the mutant lamin-A protein "progerin," features robust sterile inflammation/interferon (IFN)-like response. Targeting inflammation delays cellular and organismal HGPS phenotypes. However, specific mechanisms driving the sterile inflammation/IFN-like response and how this response causes tissue degeneration/loss in HGPS are unknown. We demonstrate that signal transducer and activator of transcription 1 (STAT1) drives the IFN-like response and aging phenotypes in HGPS cellular and mouse models. Calcitriol and baricitinib strongly repress sterile inflammation/IFN-like response, improving hallmarks of progerinexpressing cells such as mitochondrial, autophagy, and proliferation defects. In vivo, calcitriol or baricitinib extend lifespan of progeria mice, and baricitinib alone or combined with a high-caloric/high-fat diet has a remarkable impact reducing skin, aortic, and adipose tissue degeneration. Critically, Stat1 haploinsufficiency reduces tissue degeneration/loss and extends lifespan of progeria mice, recapitulating baricitinib benefits. Our study unveils STAT1 as a driver of the IFN-like response and HGPS pathology and suggests that aberrant STAT1 signaling contributes to aging, providing new therapeutic possibilities for HGPS and other inflammation/IFN response-associated diseases.