Dataset Information

NeonGreen-POLQ knock-in in Human embryonic kidney 293 cells VS Human embryonic kidney 293 cells

ABSTRACT: Replication stress (RS) can lead to the formation of DNA double strand breaks (DSBs) and threatens genomic stability. Homologous recombination (HR) pathway is essential to prevent RS and repairs associated DSBs. Upon excessive RS or HR deficiency, DSBs can persist in mitosis, wherein DNA damage response and DSB repair are inhibited. Thus, the fate of DSBs remaining or arising in mitosis remains poorly understood. Here we unwind two distinct roles of the polymerase theta (Polθ) in the maintenance of genomic stability. First, by mass spectrometry and foci screening we show that, in interphase, Polθ interacts with HR proteins and its recruitment to IR-induced DSBs is highly dependent of HR pathway. Secondly, we identify a novel role of the Polθ in counteracting the deleterious effect of DSBs in mitosis. Contrariwise to its interphase recruitment, Polθ recruitment to mitotic DSBs is HR-independent and triggered by mitotic kinases activities. In response to RS or HR deficiency, Polθ localizes to DSBs throughout mitosis and forms nuclear bodies in the G1 daughter cells. In addition, Polθ localizes to centromeres and acentric fragments and activates the mitotic checkpoint. Conversely, Polθ deficiency leads to premature anaphase onset, resulting in an accumulation of mitotic abnormalities. Strikingly, the specific inhibition of Polθ in mitosis kills HR-deficient cells, identifying mitotic Polθ function as its key role in maintaining genome integrity. Our results pinpoint to the mitotic Polθ-mediated replication stress response pathway as a unique vulnerability of cancer cells, with great potential for further investigation.

INSTRUMENT(S): Orbitrap Exploris 480

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Embryonic Kidney Cell Line

SUBMITTER: Victor Laigle

LAB HEAD: Damarys Loew

PROVIDER: PXD029585 | Pride | 2023-09-18

REPOSITORIES: Pride

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Publications

Polθ is phosphorylated by PLK1 to repair double-strand breaks in mitosis.

Gelot Camille C Kovacs Marton Tibor MT Miron Simona S Mylne Emilie E Haan Alexis A Boeffard-Dosierre Liza L Ghouil Rania R Popova Tatiana T Dingli Florent F Loew Damarys D Guirouilh-Barbat Josée J Del Nery Elaine E Zinn-Justin Sophie S Ceccaldi Raphael R

Nature 20230906 7978

DNA double-strand breaks (DSBs) are deleterious lesions that challenge genome integrity. To mitigate this threat, human cells rely on the activity of multiple DNA repair machineries that are tightly regulated throughout the cell cycle1. In interphase, DSBs are mainly repaired by non-homologous end joining and homologous recombination2. However, these pathways are completely inhibited in mitosis3-5, leaving the fate of mitotic DSBs unknown. Here we show that DNA p ...[more]

PMID: 37674080

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Project description:Mitosis entails global alterations to chromosome structure and nuclear architecture, concomitant with transient silencing of transcription. How cells transmit transcriptional states through mitosis remains incompletely understood. While many nuclear factors dissociate from mitotic chromosomes, the observation that certain nuclear factors and chromatin features remain associated with individual loci during mitosis originated the hypothesis that they could provide transcriptional memory through mitosis. To obtain the first genome-wide view of the dynamics of chromatin structure during mitosis, we compared the DNase sensitivity of interphase and mitotic chromatin at two stages of cellular maturation in a rapidly dividingmurine erythroblastmodel. Despite global chromosome condensation visible during mitosis at the microscopic level, the chromatin accessibility landscape is largely unaltered. However, mitotic chromatin accessibility is locally dynamic, with individual loci maintaining none, some, or all of their interphase accessibility. Mitotic reduction in accessibility occurs primarily within narrow, highly hypersensitive sites that frequently coincide with transcription factor binding sites, whereas broader domains of moderate accessibility tend to be more stable. In mitosis, proximal promoters generally maintain their accessibility, whereas distal regulatory elements preferentially lose accessibility. Promoters with the highest degree of accessibility preservation in mitosis tend to also be accessible across many murine tissues in interphase. Transcription factor GATA1 exerts site-specific changes in interphase accessibility that are most pronounced at distal regulatory elements, but does not visibly influence mitotic accessibility. We conclude that features of open chromatin are remarkably stable through mitosis and are modulated at the level of individual genes and regulatory elements. Dnase-Seq data is integrated with Chip-seq [GSE36589, GSE30142] and RNA-seq to examine epigentic changes in mitosis. We performed DNase-seq on two cell lines, G1E and G1E-ER4, both on an asynchronus population, and on a sample of cells in mitosis; each of the 4 experiments in triplicate.

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