RESUMO
Ubiquitin-dependent unfolding of the CMG helicase by VCP/p97 is required to terminate DNA replication. Other replisome components are not processed in the same fashion, suggesting that additional mechanisms underlie replication protein turnover. Here, we identify replisome factor interactions with a protein complex composed of AAA+ ATPases SPATA5-SPATA5L1 together with heterodimeric partners C1orf109-CINP (55LCC). An integrative structural biology approach revealed a molecular architecture of SPATA5-SPATA5L1 N-terminal domains interacting with C1orf109-CINP to form a funnel-like structure above a cylindrically shaped ATPase motor. Deficiency in the 55LCC complex elicited ubiquitin-independent proteotoxicity, replication stress, and severe chromosome instability. 55LCC showed ATPase activity that was specifically enhanced by replication fork DNA and was coupled to cysteine protease-dependent cleavage of replisome substrates in response to replication fork damage. These findings define 55LCC-mediated proteostasis as critical for replication fork progression and genome stability and provide a rationale for pathogenic variants seen in associated human neurodevelopmental disorders.
Assuntos
Adenosina Trifosfatases , Replicação do DNA , Instabilidade Genômica , Proteostase , Humanos , Adenosina Trifosfatases/metabolismo , Proteína com Valosina/metabolismo , Proteína com Valosina/genética , Células HEK293 , Proteínas de Ciclo Celular/metabolismo , ATPases Associadas a Diversas Atividades Celulares/metabolismo , ATPases Associadas a Diversas Atividades Celulares/genéticaRESUMO
The Bloom syndrome (BLM) helicase is critical for alternative lengthening of telomeres (ALT), a homology-directed repair (HDR)-mediated telomere maintenance mechanism that is prevalent in cancers of mesenchymal origin. The DNA substrates that BLM engages to direct telomere recombination during ALT remain unknown. Here, we determine that BLM helicase acts on lagging strand telomere intermediates that occur specifically in ALT-positive cells to assemble a replication-associated DNA damage response. Loss of ATRX was permissive for BLM localization to ALT telomeres in S and G2, commensurate with the appearance of telomere C-strand-specific single-stranded DNA (ssDNA). DNA2 nuclease deficiency increased 5'-flap formation in a BLM-dependent manner, while telomere C-strand, but not G-strand, nicks promoted ALT. These findings define the seminal events in the ALT DNA damage response, linking aberrant telomeric lagging strand DNA replication with a BLM-directed HDR mechanism that sustains telomere length in a subset of human cancers.
Assuntos
Dano ao DNA , Replicação do DNA , RecQ Helicases , Homeostase do Telômero , Telômero , RecQ Helicases/metabolismo , RecQ Helicases/genética , Humanos , Telômero/metabolismo , Telômero/genética , DNA de Cadeia Simples/metabolismo , DNA de Cadeia Simples/genética , Proteína Nuclear Ligada ao X/genética , Proteína Nuclear Ligada ao X/metabolismo , DNA Helicases/metabolismo , DNA Helicases/genética , Síndrome de Bloom/genética , Síndrome de Bloom/metabolismo , Síndrome de Bloom/enzimologia , Síndrome de Bloom/patologia , Linhagem Celular TumoralRESUMO
The CRL4-DCAF15 E3 ubiquitin ligase complex is targeted by the aryl-sulfonamide molecular glues, leading to neo-substrate recruitment, ubiquitination, and proteasomal degradation. However, the physiological function of DCAF15 remains unknown. Using a domain-focused genetic screening approach, we reveal DCAF15 as an acute myeloid leukemia (AML)-biased dependency. Loss of DCAF15 results in suppression of AML through compromised replication fork integrity and consequent accumulation of DNA damage. Accordingly, DCAF15 loss sensitizes AML to replication stress-inducing therapeutics. Mechanistically, we discover that DCAF15 directly interacts with the SMC1A protein of the cohesin complex and destabilizes the cohesin regulatory factors PDS5A and CDCA5. Loss of PDS5A and CDCA5 removal precludes cohesin acetylation on chromatin, resulting in uncontrolled chromatin loop extrusion, defective DNA replication, and apoptosis. Collectively, our findings uncover an endogenous, cell autonomous function of DCAF15 in sustaining AML proliferation through post-translational control of cohesin dynamics.
Assuntos
Proteínas de Ciclo Celular , Proteínas Cromossômicas não Histona , Coesinas , Dano ao DNA , Replicação do DNA , Leucemia Mieloide Aguda , Proteínas Cromossômicas não Histona/metabolismo , Proteínas Cromossômicas não Histona/genética , Humanos , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/genética , Leucemia Mieloide Aguda/metabolismo , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patologia , Linhagem Celular Tumoral , Acetilação , Animais , Proteínas Nucleares/metabolismo , Proteínas Nucleares/genética , Camundongos , Cromatina/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina-Proteína Ligases/genética , Apoptose , Proliferação de Células , Células HEK293RESUMO
Age-related microangiopathy, also known as small vessel disease (SVD), causes damage to the brain, retina, liver, and kidney. Based on the DNA damage theory of aging, we reasoned that genomic instability may underlie an SVD caused by dominant C-terminal variants in TREX1, the most abundant 3'-5' DNA exonuclease in mammals. C-terminal TREX1 variants cause an adult-onset SVD known as retinal vasculopathy with cerebral leukoencephalopathy (RVCL or RVCL-S). In RVCL, an aberrant, C-terminally truncated TREX1 mislocalizes to the nucleus due to deletion of its ER-anchoring domain. Since RVCL pathology mimics that of radiation injury, we reasoned that nuclear TREX1 would cause DNA damage. Here, we show that RVCL-associated TREX1 variants trigger DNA damage in humans, mice, and Drosophila, and that cells expressing RVCL mutant TREX1 are more vulnerable to DNA damage induced by chemotherapy and cytokines that up-regulate TREX1, leading to depletion of TREX1-high cells in RVCL mice. RVCL-associated TREX1 mutants inhibit homology-directed repair (HDR), causing DNA deletions and vulnerablility to PARP inhibitors. In women with RVCL, we observe early-onset breast cancer, similar to patients with BRCA1/2 variants. Our results provide a mechanistic basis linking aberrant TREX1 activity to the DNA damage theory of aging, premature senescence, and microvascular disease.