DNA Damage-Dependent Acetylation and Ubiquitination of H2AX Enhances Chromatin Dynamics

ABSTRACT Chromatin reorganization plays an important role in DNA repair, apoptosis, and cell cycle checkpoints. Among proteins involved in chromatin reorganization, TIP60 histone acetyltransferase has been shown to play a role in DNA repair and apoptosis. However, how TIP60 regulates chromatin reorganization in the response of human cells to DNA damage is largely unknown. Here, we show that ionizing irradiation induces TIP60 acetylation of histone H2AX, a variant form of H2A known to be phosphorylated following DNA damage. Furthermore, TIP60 regulates the ubiquitination of H2AX via the ubiquitin-conjugating enzyme UBC13, which is induced by DNA damage. This ubiquitination of H2AX requires its prior acetylation. We also demonstrate that acetylation-dependent ubiquitination by the TIP60-UBC13 complex leads to the release of H2AX from damaged chromatin. We conclude that the sequential acetylation and ubiquitination of H2AX by TIP60-UBC13 promote enhanced histone dynamics, which in turn stimulate a DNA damage response.

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Preserving protein homeostasis prevents motor impairment in DNA Damage Response-compromised C. elegans

10.1101/2021.12.22.473820 ◽

2021 ◽

Author(s):

Wouter Huiting ◽

Alejandra Duque-Jaramillo ◽

Renée Seinstra ◽

Harm Kampinga ◽

Ellen Nollen ◽

...

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Protein Aggregation ◽

Dna Damage Response ◽

Excision Repair ◽

Cell Cycle Checkpoints ◽

Protein Homeostasis ◽

Wide Range ◽

Damage Response ◽

Degenerative Processes

To maintain genome integrity, cells rely on a complex system of DNA repair pathways and cell cycle checkpoints, together referred to as the DNA damage response (DDR). Impairments in DDR pathways are linked to cancer, but also to a wide range of degenerative processes, frequently including progressive neuropathy and accelerated aging. How defects in mechanistically distinct DDR pathways can drive similar degenerative phenotypes is not understood. Here we show that defects in various DDR components are linked to a loss of protein homeostasis in Caenorhabditis elegans. Prolonged silencing of atm-1, brc-1 or ung-1, central components in respectively checkpoint signaling, double strand break repair and base excision repair enhances the global aggregation of proteins occurring in adult animals, and accelerates polyglutamine protein aggregation in a model for neurodegenerative diseases. Overexpression of the molecular chaperone HSP-16.2 prevents enhanced protein aggregation in atm-1, brc-1 or ung-1-compromised animals. Strikingly, rebalancing protein homeostasis with HSP-16.2 almost completely rescues age-associated impaired motor function in these animals as well. This reveals that the consequences of a loss of atm-1, brc-1 or ung-1 converge on an impaired protein homeostasis to cause degeneration. These findings indicate that a loss of protein homeostasis is a crucial downstream consequence of DNA repair defects, and thereby provide an attractive novel framework for understanding the broad link between DDR defects and degenerative processes.

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Dimerization of MORC2 through its C-terminal coiled-coil domain enhances chromatin dynamics and promotes DNA repair

Cell Communication and Signaling ◽

10.1186/s12964-019-0477-5 ◽

2019 ◽

Vol 17 (1) ◽

Cited By ~ 1

Author(s):

Hong-Yan Xie ◽

Tai-Mei Zhang ◽

Shu-Yuan Hu ◽

Zhi-Ming Shao ◽

Da-Qiang Li

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Cell Survival ◽

Zinc Finger Protein ◽

Coiled Coil ◽

Dna Interaction ◽

Chromatin Dynamics ◽

Histone H2ax ◽

Finger Protein ◽

Dna Repair Proteins

AbstractDecondesation of the highly compacted chromatin architecture is essential for efficient DNA repair, but how this is achieved remains largely unknown. Here, we report that microrchidia family CW-type zinc finger protein 2 (MORC2), a newly identified ATPase-dependent chromatin remodeling enzyme, is required for nucleosome destabilization after DNA damage through loosening the histone-DNA interaction. Depletion of MORC2 attenuates phosphorylated histone H2AX (γH2AX) focal formation, compromises the recruitment of DNA repair proteins, BRCA1, 53BP1, and Rad51, to sites of DNA damage, and consequently reduces cell survival following treatment with DNA-damaging chemotherapeutic drug camptothecin (CPT). Furthermore, we demonstrate that MORC2 can form a homodimer through its C-terminal coiled-coil (CC) domain, a process that is enhanced in response to CPT-induced DNA damage. Deletion of the C-terminal CC domain in MORC2 disrupts its homodimer formation and impairs its ability to destabilize histone-DNA interaction after DNA damage. Consistently, expression of dimerization-defective MORC2 mutant results in impaired the recruitment of DNA repair proteins to damaged chromatin and decreased cell survival after CPT treatment. Together, these findings uncover a new mechanism for MORC2 in modulating chromatin dynamics and DDR signaling through its c-terminal dimerization.

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DNA Damage Response in Multiple Myeloma: The Role of the Tumor Microenvironment

Cancers ◽

10.3390/cancers13030504 ◽

2021 ◽

Vol 13 (3) ◽

pp. 504

Author(s):

Takayuki Saitoh ◽

Tsukasa Oda

Keyword(s):

Multiple Myeloma ◽

Dna Damage ◽

Dna Repair ◽

Tumor Microenvironment ◽

Dna Damage Response ◽

Genetic Instability ◽

Dna Repair Mechanisms ◽

Damage Response ◽

Repair Mechanisms

Multiple myeloma (MM) is an incurable plasma cell malignancy characterized by genomic instability. MM cells present various forms of genetic instability, including chromosomal instability, microsatellite instability, and base-pair alterations, as well as changes in chromosome number. The tumor microenvironment and an abnormal DNA repair function affect genetic instability in this disease. In addition, states of the tumor microenvironment itself, such as inflammation and hypoxia, influence the DNA damage response, which includes DNA repair mechanisms, cell cycle checkpoints, and apoptotic pathways. Unrepaired DNA damage in tumor cells has been shown to exacerbate genomic instability and aberrant features that enable MM progression and drug resistance. This review provides an overview of the DNA repair pathways, with a special focus on their function in MM, and discusses the role of the tumor microenvironment in governing DNA repair mechanisms.

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Harnessing the Nucleolar DNA Damage Response in Cancer Therapy

Genes ◽

10.3390/genes12081156 ◽

2021 ◽

Vol 12 (8) ◽

pp. 1156

Author(s):

Jiachen Xuan ◽

Kezia Gitareja ◽

Natalie Brajanovski ◽

Elaine Sanij

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Cancer Therapy ◽

Dna Damage Response ◽

Rrna Genes ◽

Rrna Synthesis ◽

Pol I ◽

Clinical Investigations ◽

Damage Response ◽

Synthesis And Processing

The nucleoli are subdomains of the nucleus that form around actively transcribed ribosomal RNA (rRNA) genes. They serve as the site of rRNA synthesis and processing, and ribosome assembly. There are 400–600 copies of rRNA genes (rDNA) in human cells and their highly repetitive and transcribed nature poses a challenge for DNA repair and replication machineries. It is only in the last 7 years that the DNA damage response and processes of DNA repair at the rDNA repeats have been recognized to be unique and distinct from the classic response to DNA damage in the nucleoplasm. In the last decade, the nucleolus has also emerged as a central hub for coordinating responses to stress via sequestering tumor suppressors, DNA repair and cell cycle factors until they are required for their functional role in the nucleoplasm. In this review, we focus on features of the rDNA repeats that make them highly vulnerable to DNA damage and the mechanisms by which rDNA damage is repaired. We highlight the molecular consequences of rDNA damage including activation of the nucleolar DNA damage response, which is emerging as a unique response that can be exploited in anti-cancer therapy. In this review, we focus on CX-5461, a novel inhibitor of Pol I transcription that induces the nucleolar DNA damage response and is showing increasing promise in clinical investigations.

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The DNA damage inducible lncRNA SCAT7 regulates genomic integrity and topoisomerase 1 turnover in lung adenocarcinoma

NAR Cancer ◽

10.1093/narcan/zcab002 ◽

2021 ◽

Vol 3 (1) ◽

Author(s):

Luisa Statello ◽

Mohamad M Ali ◽

Silke Reischl ◽

Sagar Mahale ◽

Subazini Thankaswamy Kosalai ◽

...

Keyword(s):

Dna Damage ◽

Dna Damage Response ◽

Cancer Biology ◽

Topoisomerase I ◽

Cell Cycle Checkpoints ◽

Topoisomerase 1 ◽

Damage Response ◽

Promote Cell Survival

Abstract Despite the rapid improvements in unveiling the importance of lncRNAs in all aspects of cancer biology, there is still a void in mechanistic understanding of their role in the DNA damage response. Here we explored the potential role of the oncogenic lncRNA SCAT7 (ELF3-AS1) in the maintenance of genome integrity. We show that SCAT7 is upregulated in response to DNA-damaging drugs like cisplatin and camptothecin, where SCAT7 expression is required to promote cell survival. SCAT7 silencing leads to decreased proliferation of cisplatin-resistant cells in vitro and in vivo through interfering with cell cycle checkpoints and DNA repair molecular pathways. SCAT7 regulates ATR signaling, promoting homologous recombination. Importantly, SCAT7 also takes part in proteasome-mediated topoisomerase I (TOP1) degradation, and its depletion causes an accumulation of TOP1–cc structures responsible for the high levels of intrinsic DNA damage. Thus, our data demonstrate that SCAT7 is an important constituent of the DNA damage response pathway and serves as a potential therapeutic target for hard-to-treat drug resistant cancers.

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Female ageing affects the DNA repair capacity of oocytes in IVF using a controlled model of sperm DNA damage in mice

Human Reproduction ◽

10.1093/humrep/dez308 ◽

2020 ◽

Vol 35 (3) ◽

pp. 529-544 ◽

Cited By ~ 6

Author(s):

F Horta ◽

S Catt ◽

P Ramachandran ◽

B Vollenhoven ◽

P Temple-Smith

Keyword(s):

Gene Expression ◽

Dna Damage ◽

Dna Repair ◽

Age Groups ◽

Oocyte Quality ◽

Repair Capacity ◽

Sperm Dna Damage ◽

Dna Repair Capacity ◽

Sperm Dna ◽

Damage Response

Abstract STUDY QUESTION Does female ageing have a negative effect on the DNA repair capacity of oocytes fertilised by spermatozoa with controlled levels of DNA damage? SUMMARY ANSWER Compared to oocytes from younger females, oocytes from older females have a reduced capacity to repair damaged DNA introduced by spermatozoa. WHAT IS KNOWN ALREADY The reproductive lifespan in women declines with age predominantly due to poor oocyte quality. This leads to decreased reproductive outcomes for older women undergoing assisted reproductive technology (ART) treatments, compared to young women. Ageing and oocyte quality have been clearly associated with aneuploidy, but the range of factors that influence this change in oocyte quality with age remains unclear. The DNA repair activity prior to embryonic genomic activation is considered to be of maternal origin, with maternal transcripts and proteins controlling DNA integrity. With increasing maternal age, the number of mRNAs stored in oocytes decreases. This could result in diminished efficiency of DNA repair and/or negative effects on embryo development, especially in the presence of DNA damage. STUDY DESIGN, SIZE, DURATION Oocytes from two age groups of 30 super-ovulated female mice (young: 5–8 weeks old, n = 15; old: 42–45 weeks old, n = 15) were inseminated with sperm from five males with three different controlled DNA damage levels; control: ≤10%, 1 Gray (Gy): 11–30%, and 30 Gy: >30%. Inseminated oocytes (young: 125, old: 78) were assessed for the formation of zygotes (per oocyte) and blastocysts (per zygote). Five replicates of five germinal vesicles (GVs) and five MII oocytes from each age group were analysed for gene expression. The DNA damage response (DDR) was assessed in a minimum of three IVF replicates in control and 1 Gy zygotes and two-cell embryos using γH2AX labelling. PARTICIPANTS/MATERIALS, SETTING, METHODS Swim-up sperm samples from the cauda epididymidis of C57BL6 mice were divided into control (no irradiation) and 1- and 30-Gy groups. Treated spermatozoa were irradiated at 1 and 30 Gy, respectively, using a linear accelerator Varian 21iX. Following irradiation, samples were used for DNA damage assessment (Halomax) and for insemination. Presumed zygotes were cultured in a time-lapse incubator (MIRI, ESCO). Gene expression of 91 DNA repair genes was assessed using the Fluidigm Biomark HD system. The DNA damage response in zygotes (6–8 h post-fertilisation) and two-cell embryos (22–24 h post-fertilisation) was assessed by immunocytochemical analysis of γH2AX using confocal microscopy (Olympus FV1200) and 3D volumetric analysis using IMARIS software. MAIN RESULTS AND THE ROLE OF CHANCE The average sperm DNA damage for the three groups was statistically different (control: 6.1%, 1 Gy: 16.1%, 30 Gy: 53.1%, P < 0.0001), but there were no significant differences in fertilisation rates after IVF within or between the two age groups [(young; control: 86.79%, 1 Gy: 82.75%, 30 Gy: 76.74%) (old; control: 93.1%, 1 Gy: 70.37%, 30 Gy: 68.18%) Fisher’s exact]. However, blastocyst rates were significantly different (P < 0.0001) among the groups [(young; control: 86.95%, 1 Gy: 33.33%, 30 Gy: 0.0%) (old; control: 70.37%, 1 Gy: 0.0%, 30 Gy: 0.0%)]. Between the age groups, 1-Gy samples showed a significant decrease in the blastocyst rate in old females compared to young females (P = 0.0166). Gene expression analysis revealed a decrease in relative expression of 21 DNA repair genes in old GV oocytes compared to young GV oocytes (P < 0.05), and similarly, old MII oocytes showed 23 genes with reduced expression compared to young MII oocytes (P < 0.05). The number of genes with decreased expression in older GV and MII oocytes significantly affected pathways such as double strand break (GV: 5; MII: 6), nucleotide excision repair (GV: 8; MII: 5) and DNA damage response (GV: 4; MII: 8). There was a decreased DDR in zygotes and in two-cell embryos from old females compared to young regardless of sperm treatment (P < 0.05). The decrease in DNA repair gene expression of oocytes and decreased DDR in embryos derived from older females suggests that ageing results in a diminished DNA repair capacity. LARGE-SCALE DATA N/A LIMITATIONS, REASONS FOR CAUTION Ionising radiation was used only for experimental purposes, aiming at controlled levels of sperm DNA damage; however, it can also damage spermatozoa proteins. The female age groups selected in mice were intended to model effects in young and old women, but clinical studies are required to demonstrate a similar effect. WIDER IMPLICATIONS OF THE FINDINGS Fertilisation can occur with sperm populations with medium and high DNA damage, but subsequent embryo growth is affected to a greater extent with aging females, supporting the theory that oocyte DNA repair capacity decreases with age. Assessment of the oocyte DNA repair capacity may be a useful diagnostic tool for infertile couples. STUDY FUNDING/COMPETING INTEREST(S) Funded by the Education Program in Reproduction and Development, Department of Obstetrics and Gynaecology, Monash University. None of the authors has any conflict of interest to report.

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Profilin-1; a novel regulator of DNA damage response and repair machinery in keratinocytes

Molecular Biology Reports ◽

10.1007/s11033-021-06210-6 ◽

2021 ◽

Author(s):

Chang-Jin Lee ◽

Min-Ji Yoon ◽

Dong Hyun Kim ◽

Tae Uk Kim ◽

Youn-Jung Kang

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Dna Damage Response ◽

Recovery Time ◽

Actin Polymerization ◽

Loss Of Function ◽

Dna Double Strand Breaks ◽

Pten Loss ◽

Damage Response ◽

Specific Regulation

AbstractProfilin-1 (PFN1) regulates actin polymerization and cytoskeletal growth. Despite the essential roles of PFN1 in cell integration, its subcellular function in keratinocyte has not been elucidated yet. Here we characterize the specific regulation of PFN1 in DNA damage response and repair machinery. PFN1 depletion accelerated DNA damage-mediated apoptosis exhibiting PTEN loss of function instigated by increased phosphorylated inactivation followed by high levels of AKT activation. PFN1 changed its predominant cytoplasmic localization to the nucleus upon DNA damage and subsequently restored the cytoplasmic compartment during the recovery time. Even though γH2AX was recruited at the sites of DNA double strand breaks in response to DNA damage, PFN1-deficient cells failed to recruit DNA repair factors, whereas control cells exhibited significant increases of these genes. Additionally, PFN1 depletion resulted in disruption of PTEN-AKT cascade upon DNA damage and CHK1-mediated cell cycle arrest was not recovered even after the recovery time exhibiting γH2AX accumulation. This might suggest PFN1 roles in regulating DNA damage response and repair machinery to protect cells from DNA damage. Future studies addressing the crosstalk and regulation of PTEN-related DNA damage sensing and repair pathway choice by PFN1 may further aid to identify new mechanistic insights for various DNA repair disorders.

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900 Depleting non-canonical, cell-intrinsic PD-L1 signals induces synthetic lethality to small molecule DNA damage response inhibitors in an immune independent and dependent manner

Journal for ImmunoTherapy of Cancer ◽

10.1136/jitc-2021-sitc2021.900 ◽

2021 ◽

Vol 9 (Suppl 3) ◽

pp. A944-A944

Author(s):

Anand Kornepati ◽

Clare Murray ◽

Barbara Avalos ◽

Cody Rogers ◽

Kavya Ramkumar ◽

...

Keyword(s):

Ovarian Cancer ◽

Dna Damage ◽

Dna Repair ◽

Cell Lines ◽

Dna Damage Response ◽

Small Molecule ◽

Treatment Resistance ◽

Programmed Death ◽

Damage Response ◽

Response Biomarker

BackgroundTumor surface-expressed programmed death-ligand 1 (PD-L1) suppresses immunity when it engages programmed death-1 (PD-1) on anti-tumor immune cells in canonical PD-L1/PD-1.1 Non-canonical, tumour-intrinsic PD-L1 signals can mediate treatment resistance2–6 but mechanisms remain incompletely understood. Targeting non-canonical, cell-intrinsic PD-L1 signals, especially modulation of the DNA damage response (DDR), remains largely untapped.MethodsWe made PD-L1 knockout (PD-L1 KO) murine transplantable and human cell lines representing melanoma, bladder, and breast histologies. We used biochemical, genetic, and cell-biology techniques for mechanistic insights into tumor-intrinsic PD-L1 control of specific DDR and DNA repair pathways. We generated a novel inducible melanoma GEMM lacking PD-L1 only in melanocytes to corroborate DDR alterations observed in PD-L1 KO of established tumors.ResultsGenetic tumor PD-L1 depletion destabilized Chk2 and impaired ATM/Chk2, but not ATR/Chk1 DDR. PD-L1KO increased DNA damage (γH2AX) and impaired homologous recombination DNA repair (p-RPA32, BRCA1, RAD51 nuclear foci) and function (DR-GFP reporter). PD-L1 KO cells were significantly more sensitive versus controls to DDR inhibitors (DDRi) against ATR, Chk1, and PARP but not ATM in multiple human and mouse tumor models in vitro and in vivo in NSG mice. PD-1 independent, intracellular, not surface PD-L1 stabilized Chk2 protein with minimal Chek2 mRNA effect. Mechanistically, PD-L1 could directly complex with Chk2, protecting it from PIRH2-mediated polyubiquitination. PD-L1 N-terminal domains Ig-V and Ig-C but not the PD-L1 C-terminal tail co-IP’d with Chk2 and restored Chk1 inhibitor (Chk1i) treatment resistance. Tumor PD-L1 expression correlated with Chk1i sensitivity in 44 primary human small cell lung cancer cell lines, implicating tumor-intrinsic PD-L1 as a DDRi response biomarker. In WT mice, genetic PD-L1 depletion but not surface PD-L1 blockade with αPD-L1, sensitized immunotherapy-resistant, BRCA1-WT 4T1 tumors to PARP inhibitor (PARPi). PARPi effects were reduced on PD-L1 KO tumors in RAG2KO mice indicating immune-dependent DDRi efficacy. Tumor PD-L1 depletion, likely due to impaired DDR, enhanced PARPi induced tumor-intrinsic STING activation (e.g., p-TBK1, CCL5) suggesting potential to augment immunotherapies.ConclusionsWe challenge the prevailing surface PD-L1 paradigm and establish a novel mechanism for cell-intrinsic PD-L1 control of the DDR and gene product expression. We identify therapeutic vulnerabilities from tumor PD-L1 depletion utilizing small molecule DDRi currently being tested in clinical trials. Data could explain αPD-L1/DDRi treatment resistance. Intracellular PD-L1 could be a pharmacologically targetable treatment target and/or response biomarker for selective DDRi alone plus other immunotherapies.ReferencesTopalian SL, Taube JM, Anders RA, Pardoll DM. Mechanism-driven biomarkers to guide immune checkpoint blockade in cancer therapy. Nat Rev Cancer 16:275–287, doi:10.1038/nrc.2016.36 (2016).Clark CA, et al. Tumor-intrinsic PD-L1 signals regulate cell growth, pathogenesis and autophagy in ovarian cancer and melanoma. Canres 0258.2016 (2016).Gupta HB et al. Tumor cell-intrinsic PD-L1 promotes tumor-initiating cell generation and functions in melanoma and ovarian cancer. 1, 16030 (2016).Zhu H, et al. BET bromodomain inhibition promotes anti-tumor immunity by suppressing PD-L1 expression. Cell Rep 16:2829–2837, doi:10.1016/j.celrep.2016.08.032 (2016)Wu B, et al. Adipose PD-L1 modulates PD-1/PD-L1 checkpoint blockade immunotherapy efficacy in breast cancer. Oncoimmunology 7:e1500107, doi:10.1080/2162402X.2018.1500107 (2018)Liang J, et al. Verteporfin inhibits PD-L1 through autophagy and the STAT1-IRF1-TRIM28 signaling axis, exerting antitumor efficacy. Cancer Immunol Res 8:952–965, doi:10.1158/2326-6066.CIR-19-0159 (2020)

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Mutant huntingtin impairs PNKP and ATXN3, disrupting DNA repair and transcription

eLife ◽

10.7554/elife.42988 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 15

Author(s):

Rui Gao ◽

Anirban Chakraborty ◽

Charlene Geater ◽

Subrata Pradhan ◽

Kara L Gordon ◽

...

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Rna Polymerase Ii ◽

Dna Damage Response ◽

Functional Decline ◽

Transcriptional Elongation ◽

Damage Repair ◽

Damage Response ◽

Cyclic Amp Response Element ◽

Atm Signaling

How huntingtin (HTT) triggers neurotoxicity in Huntington’s disease (HD) remains unclear. We report that HTT forms a transcription-coupled DNA repair (TCR) complex with RNA polymerase II subunit A (POLR2A), ataxin-3, the DNA repair enzyme polynucleotide-kinase-3'-phosphatase (PNKP), and cyclic AMP-response element-binding (CREB) protein (CBP). This complex senses and facilitates DNA damage repair during transcriptional elongation, but its functional integrity is impaired by mutant HTT. Abrogated PNKP activity results in persistent DNA break accumulation, preferentially in actively transcribed genes, and aberrant activation of DNA damage-response ataxia telangiectasia-mutated (ATM) signaling in HD transgenic mouse and cell models. A concomitant decrease in Ataxin-3 activity facilitates CBP ubiquitination and degradation, adversely impacting transcription and DNA repair. Increasing PNKP activity in mutant cells improves genome integrity and cell survival. These findings suggest a potential molecular mechanism of how mutant HTT activates DNA damage-response pro-degenerative pathways and impairs transcription, triggering neurotoxicity and functional decline in HD.

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Division of Labor between SOS and PafBC in Mycobacterial DNA Repair and Mutagenesis

10.1101/2021.08.05.455301 ◽

2021 ◽

Author(s):

Oyindamola O Adefisayo ◽

Pierre Dupuy ◽

James M Bean ◽

Michael S Glickman

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Antibiotic Resistance ◽

Division Of Labor ◽

Transcriptional Regulatory Network ◽

Lexa Repressor ◽

Quinolone Antibiotics ◽

Transcriptional Regulatory ◽

Damage Response ◽

Insight Into

DNA repair systems allow microbes to survive in diverse environments that compromise chromosomal integrity. Pathogens such as M. tuberculosis must contend with the genotoxic host environment, which generates the mutations that underlie antibiotic resistance. Mycobacteria encode the widely distributed SOS pathway, governed by the LexA repressor, but also encode PafBC, a positive regulator of the transcriptional DNA damage response (DDR). Although the transcriptional outputs of these systems have been characterized, their full functional division of labor in survival and mutagenesis is unknown. Here we specifically ablate the PafBC or SOS pathways, alone and in combination, and test their relative contributions to repair. We find that SOS and PafBC have both distinct and overlapping roles that depend on the type of DNA damage. Most notably, we find that quinolone antibiotics and replication fork perturbation are inducers of the PafBC pathway, and that chromosomal mutagenesis is codependent on PafBC and SOS, through shared regulation of the DnaE2/ImuA/B mutasome. These studies define the complex transcriptional regulatory network of the DDR in mycobacteria and provide new insight into the regulatory mechanisms controlling the genesis of antibiotic resistance in M. tuberculosis.

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