More Like this

1. Rescue of DNA damage after constricted migration reveals a mechano-regulated threshold for cell cycle

   https://doi.org/10.1083/jcb.201811100  

   Xia, Yuntao; Pfeifer, Charlotte R.; Zhu, Kuangzheng; Irianto, Jerome; Liu, Dazhen; Pannell, Kalia; Chen, Emily J.; Dooling, Lawrence J.; Tobin, Michael P.; Wang, Mai; et al (August 2019, The Journal of Cell Biology)

   Migration through 3D constrictions can cause nuclear rupture and mislocalization of nuclear proteins, but damage to DNA remains uncertain, as does any effect on cell cycle. Here, myosin II inhibition rescues rupture and partially rescues the DNA damage marker γH2AX, but an apparent block in cell cycle appears unaffected. Co-overexpression of multiple DNA repair factors or antioxidant inhibition of break formation also exert partial effects, independently of rupture. Combined treatments completely rescue cell cycle suppression by DNA damage, revealing a sigmoidal dependence of cell cycle on excess DNA damage. Migration through custom-etched pores yields the same damage threshold, with ∼4-µm pores causing intermediate levels of both damage and cell cycle suppression. High curvature imposed rapidly by pores or probes or else by small micronuclei consistently associates nuclear rupture with dilution of stiff lamin-B filaments, loss of repair factors, and entry from cytoplasm of chromatin-binding cGAS (cyclic GMP-AMP synthase). The cell cycle block caused by constricted migration is nonetheless reversible, with a potential for DNA misrepair and genome variation. 

   more » « less
2. ATM Modulates Nuclear Mechanics by Regulating Lamin A Levels

   https://doi.org/10.3389/fcell.2022.875132  

   Shah, Pragya; McGuigan, Connor W.; Cheng, Svea; Vanpouille-Box, Claire; Demaria, Sandra; Weiss, Robert S.; Lammerding, Jan (June 2022, Frontiers in Cell and Developmental Biology)

   Ataxia-telangiectasia mutated (ATM) is one of the three main apical kinases at the crux of DNA damage response and repair in mammalian cells. ATM activates a cascade of downstream effector proteins to regulate DNA repair and cell cycle checkpoints in response to DNA double-strand breaks. While ATM is predominantly known for its role in DNA damage response and repair, new roles of ATM have recently begun to emerge, such as in regulating oxidative stress or metabolic pathways. Here, we report the surprising discovery that ATM inhibition and deletion lead to reduced expression of the nuclear envelope protein lamin A. Lamins are nuclear intermediate filaments that modulate nuclear shape, structure, and stiffness. Accordingly, inhibition or deletion of ATM resulted in increased nuclear deformability and enhanced cell migration through confined spaces, which requires substantial nuclear deformation. These findings point to a novel connection between ATM and lamin A and may have broad implications for cells with ATM mutations—as found in patients suffering from Ataxia Telangiectasia and many human cancers—which could lead to enhanced cell migration and increased metastatic potential. 

   more » « less
3. Chromosomes remain individualized through interphase in embryos of the tardigrade Hypsibius exemplaris

   https://doi.org/10.1091/mbc.E25-07-0356  

   Papell, Lillian D; Coke, Adriana N; de_Jesus, Bailey N; Harry, Clayton J; Zhang, Pu; Goldstein, Bob (January 2026, Molecular Biology of the Cell)

   Onishi, Masayuki (Ed.)

   Tardigrades are microscopic animals that can survive exceptional levels of ionizing radiation or desiccation—DNA-damaging conditions that would kill most animals. Irradiation or radiomimetic drug treatment of the tardigrade Hypsibius exemplaris can induce remarkably high expression levels of DNA repair genes, primarily those in the base excision repair and nonhomologous end joining pathways. How tardigrades can repair widespread DNA damage without producing frequent, large-scale chromosome structural abnormalities, like chromosome translocations and fusions, is unknown. Here, we report the results of examining chromosome and nuclear architecture throughout the cell cycle in early embryos of H. exemplaris. We found that H. exemplaris chromosomes are maintained in an individualized form throughout the cell cycle. We were surprised to also find that each chromosome is housed in a fully or partially separate lamin-lined compartment, instead of all chromosomes being housed in a single, nearly spherical nuclear lamina and envelope. Our results reveal unusual chromosomal and nuclear organization in a tardigrade. We speculate that these unexpected features might limit chromosomal rearrangements during DNA damage repair in extreme conditions. 

   more » « less
4. Very fast CRISPR on demand

   https://doi.org/10.1126/science.aay8204  

   Liu, Yang; Zou, Roger S.; He, Shuaixin; Nihongaki, Yuta; Li, Xiaoguang; Razavi, Shiva; Wu, Bin; Ha, Taekjip (June 2020, Science)

   CRISPR-Cas systems provide versatile tools for programmable genome editing. Here, we developed a caged RNA strategy that allows Cas9 to bind DNA but not cleave until light-induced activation. This approach, referred to as very fast CRISPR (vfCRISPR), creates double-strand breaks (DSBs) at the submicrometer and second scales. Synchronized cleavage improved kinetic analysis of DNA repair, revealing that cells respond to Cas9-induced DSBs within minutes and can retain MRE11 after DNA ligation. Phosphorylation of H2AX after DNA damage propagated more than 100 kilobases per minute, reaching up to 30 megabases. Using single-cell fluorescence imaging, we characterized multiple cycles of 53BP1 repair foci formation and dissolution, with the first cycle taking longer than subsequent cycles and its duration modulated by inhibition of repair. Imaging-guided subcellular Cas9 activation further facilitated genomic manipulation with single-allele resolution. vfCRISPR enables DNA-repair studies at high resolution in space, time, and genomic coordinates. 

   more » « less
5. The epigenetic landscape shapes smoking-induced mutagenesis by modulating DNA damage susceptibility and repair efficiency

   https://doi.org/10.1093/nar/gkaf048  

   Heilbrun, Elisheva E; Tseitline, Dana; Wasserman, Hana; Kirshenbaum, Ayala; Cohen, Yuval; Gordan, Raluca; Adar, Sheera (February 2025, Nucleic Acids Research)

   Abstract Lung cancer sequencing efforts have uncovered mutational signatures that are attributed to exposure to the cigarette smoke carcinogen benzo[a]pyrene. Benzo[a]pyrene metabolizes in cells to benzo[a]pyrene diol epoxide (BPDE) and reacts with guanine nucleotides to form bulky BPDE adducts. These DNA adducts block transcription and replication, compromising cell function and survival, and are repaired in human cells by the nucleotide excision repair pathway. Here, we applied high-resolution genomic assays to measure BPDE-induced damage formation and mutagenesis in human cells. We integrated the new damage and mutagenesis data with previous repair, DNA methylation, RNA expression, DNA replication, and chromatin component measurements in the same cell lines, along with lung cancer mutagenesis data. BPDE damage formation is significantly enhanced by DNA methylation and in accessible chromatin regions, including transcribed and early-replicating regions. Binding of transcription factors is associated primarily with reduced, but also enhanced damage formation, depending on the factor. While DNA methylation does not appear to influence repair efficiency, this repair was significantly elevated in accessible chromatin regions, which accumulated fewer mutations. Thus, when damage and repair drive mutagenesis in opposing directions, the final mutational patterns appear to be dictated by the efficiency of repair rather than the frequency of underlying damages. 

   more » « less