Abstract
Progerin accumulation disrupts nuclear lamina integrity and causes nuclear structure abnormalities, leading to premature aging, that is, Hutchinson–Gilford progeria syndrome (HGPS). The roles of nuclear subcompartments, such as PML nuclear bodies (PML NBs), in HGPS pathogenesis, are unclear. Here, we show that classical dot‐like PML NBs are reorganized into thread‐like structures in HGPS patient fibroblasts and their presence is associated with late stage of senescence. By co‐immunoprecipitation analysis, we show that farnesylated Progerin interacts with human PML2, which accounts for the formation of thread‐like PML NBs. Specifically, human PML2 but not PML1 overexpression in HGPS cells promotes PML thread development and accelerates senescence. Further immunofluorescence microscopy, immuno‐TRAP, and deep sequencing data suggest that these irregular PML NBs might promote senescence by perturbing NB‐associated DNA repair and gene expression in HGPS cells. These data identify irregular structures of PML NBs in senescent HGPS cells and support that the thread‐like PML NBs might be a novel, morphological, and functional biomarker of late senescence.
Highlights
Promyelocytic leukemia (PML) was originally identified as a fusion oncoprotein with retinoic acid receptor α (RARα)
We identified thread-like PML nuclear bodies (PML NBs) as a more definitive morphological and functional marker of senescence in Hutchinson–Gilford progeria syndrome (HGPS) cells
We found that most HGPS cells with thread-like PML NBs are SA-β-gal-positive but Ki-67-negative, express relatively lower levels of LAP2β, H3K27me3, and Lamin B1, and contain more persistent γH2AX foci
Summary
Promyelocytic leukemia (PML) was originally identified as a fusion oncoprotein with retinoic acid receptor α (RARα). We believe that it is reasonable to define HGPS cells with thread-like PML NBs, most of which are SA-β-gal-positive but Ki-67-negative, express relatively low levels of LAP2β, H3K27me, and Lamin B1, and contain a higher number of persistent γH2AX foci, as a state of late senescence Such thread-like PML NBs were observed in ~7% of late-passage normal human dermal fibroblasts (NHDFs) (Figure 1b and Figure S1c). The percentage of Ki-67-positive cells decreased, while the number of γH2AX foci increased in NHDF and HGPS cells expressing GFP-PML2 compared with GFP-PML1, especially in cells with thread-like NBs (Figure 4f,g, and Figure S3a,b). After X-ray irradiation, 1.44-fold higher number of γH2AX foci remained in HGPS cells expressing GFP-PML2 compared with that of GFP-PML1, again suggesting defective DNA repair (Figure 4h, and Figure S3c,d). These data suggest that an aberrant Progerin–PML2 association disrupts the PML NB-gene signature in HGPS cells
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