Impact of Different Types Photon Radiation on DNA Double-strand Breaks Repair Process in Microglial Cells

(Macro)autophagy delivers cellular constituents to lysosomes for degradation. Although a cytoplasmic process, autophagy-deficient cells accumulate genomic damage, but an explanation for this effect is currently unclear. We report here that inhibition of autophagy causes elevated proteasomal activity leading to enhanced degradation of checkpoint kinase 1 (Chk1), a pivotal factor for the error-free DNA repair process, homologous recombination (HR). We show that loss of autophagy critically impairs HR and that autophagy-deficient cells accrue micronuclei and sub-G1 DNA, indicators of diminished genomic integrity. Moreover, due to impaired HR, autophagy-deficient cells are hyperdependent on nonhomologous end joining (NHEJ) for repair of DNA double-strand breaks. Consequently, inhibition of NHEJ following DNA damage in the absence of autophagy results in persistence of genomic lesions and rapid cell death. Because autophagy deficiency occurs in several diseases, these findings constitute an important link between autophagy and DNA repair and highlight a synthetic lethal strategy to kill autophagy-deficient cells.

Download Full-text

Role of PRKDC in cancer initiation, progression, and treatment

Cancer Cell International ◽

10.1186/s12935-021-02229-8 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Yu Chen ◽

Yi Li ◽

Jiani Xiong ◽

Bin Lan ◽

Xuefeng Wang ◽

...

Keyword(s):

Checkpoint Inhibitors ◽

Double Strand Breaks ◽

Nonhomologous End Joining ◽

Dna Double Strand Breaks ◽

End Joining ◽

Strand Breaks ◽

Cancer Initiation ◽

Different Types ◽

Dependent Protein

AbstractThe PRKDC gene encodes the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) protein. DNA-PKcs plays an important role in nonhomologous end joining (NHEJ) of DNA double-strand breaks (DSBs) and is also closely related to the establishment of central immune tolerance and the maintenance of chromosome stability. The occurrence and development of different types of tumors and the results of their treatment are also influenced by DNA-PKcs, and it may also predict the results of radiotherapy, chemotherapy, and therapy with immune checkpoint inhibitors (ICIs). Here, we discuss and review the structure and mechanism of action of PRKDC and DNA-PKcs and their relationship with cancer.

Download Full-text

Recruitment of Scc2/4 to double strand breaks depends on γH2A and DNA end resection

10.1101/2021.07.09.451733 ◽

2021 ◽

Author(s):

Martin Scherzer ◽

Fosco Giordano ◽

Maria Sol&eacute Ferran ◽

Lena Str&oumlm

Keyword(s):

De Novo ◽

Repair Process ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Dna End Resection ◽

A Site ◽

The Impact ◽

End Resection

Homologous recombination (HR) enables cells to overcome the threat of DNA double strand breaks (DSB), allowing for repair without the loss of genetic information. Central to the HR repair process is the de novo loading of Cohesin around a DSB by its loader complex Scc2/4. Although Cohesin′s accumulation at these sites has been well studied, the prerequisites leading to Scc2/4 recruitment during the repair process are still elusive. Here we investigate which factors are required for recruitment of Scc2 around DSBs in Saccharomyces cerevisiae. To address this question, we combined ChIP-qPCR with a GAL-inducible HO-endonuclease system to generate a site specific DSB in vivo. We find that Scc2 recruitment relies on γH2A and Tel1, but as opposed to Cohesin, not on Mec1. We further demonstrate that binding of Scc2 depends on and coincides with DNA end resection. Although affected by the impact on resection, this recruitment of Scc2 is not directly facilitated by the RSC, SWR1 or INO80 complexes. Our results shed light on the intricate DSB repair cascade leading to the recruitment of Scc2/4 and the subsequent loading of Cohesin.

Download Full-text

Dot1L-dependent H3K79 methylation facilitates histone variant H2A.Z exchange at DNA double strand breaks and is required for high fidelity, homology-directed DNA repair

10.1101/544981 ◽

2019 ◽

Author(s):

Nehemiah S. Alvarez ◽

Pavla Brachova ◽

Timothy A. Fields ◽

Patrick E. Fields

Keyword(s):

Dna Repair ◽

Genome Stability ◽

Repair Process ◽

Histone Variant ◽

Double Strand Breaks ◽

Open Chromatin ◽

High Fidelity ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Non Homologous End Joining

AbstractIn eukaryotic cells, the homology-directed repair (HDR) and non-homologous end joining (NHEJ) pathways are required for the repair of DNA double strand breaks (DSB). The high-fidelity HDR pathway is particularly important for maintenance of genomic stability. In mammals, histone post-translational modifications and histone variant exchange into nucleosomes at sites of DSB generate an open chromatin state necessary for repair to take place. However, the specific contributions of histone modifications to histone variant exchange at DSB sites and the influence of these changes on the DNA repair process and genome stability are incompletely understood. Here we show that Dot1L-catalyzed methylation of H3 histone on lysine 79 (H3K79) is required for efficient HDR of DSB. In cells with DNA DSB either lacking Dot1L or expressing a methylation-dead Dot1L, there is altered kinetics of DNA repair factor recruitment, markedly decreased H2A.Z incorporation at DSB sites, and a specific and profound reduction in HDR, which results in significant genomic instability. These findings demonstrate a new role for Dot1L, identifying it as a critical regulator of the DNA repair process and a steward of genomic integrity.

Download Full-text

Repair pathway choice for double-strand breaks

Essays in Biochemistry ◽

10.1042/ebc20200007 ◽

2020 ◽

Vol 64 (5) ◽

pp. 765-777 ◽

Cited By ~ 2

Author(s):

Yixi Xu ◽

Dongyi Xu

Keyword(s):

Cell Cycle ◽

Double Strand Breaks ◽

Homologous Region ◽

Gene Repair ◽

Repair Pathway ◽

Dna Double Strand Breaks ◽

Environmental Radiation ◽

Strand Breaks ◽

Dna End Resection ◽

End Resection

Abstract Deoxyribonucleic acid (DNA) is at a constant risk of damage from endogenous substances, environmental radiation, and chemical stressors. DNA double-strand breaks (DSBs) pose a significant threat to genomic integrity and cell survival. There are two major pathways for DSB repair: nonhomologous end-joining (NHEJ) and homologous recombination (HR). The extent of DNA end resection, which determines the length of the 3′ single-stranded DNA (ssDNA) overhang, is the primary factor that determines whether repair is carried out via NHEJ or HR. NHEJ, which does not require a 3′ ssDNA tail, occurs throughout the cell cycle. 53BP1 and the cofactors PTIP or RIF1-shieldin protect the broken DNA end, inhibit long-range end resection and thus promote NHEJ. In contrast, HR mainly occurs during the S/G2 phase and requires DNA end processing to create a 3′ tail that can invade a homologous region, ensuring faithful gene repair. BRCA1 and the cofactors CtIP, EXO1, BLM/DNA2, and the MRE11–RAD50–NBS1 (MRN) complex promote DNA end resection and thus HR. DNA resection is influenced by the cell cycle, the chromatin environment, and the complexity of the DNA end break. Herein, we summarize the key factors involved in repair pathway selection for DSBs and discuss recent related publications.

Download Full-text