RESUMEN
DNA replication through a challenging genomic landscape is coordinated by the replisome, which must adjust to local conditions to provide appropriate replication speed and respond to lesions that hinder its progression. We have previously shown that proteasome shuttle proteins, DNA Damage Inducible 1 and 2 (DDI1/2), regulate Replication Termination Factor 2 (RTF2) levels at stalled replisomes, allowing fork stabilization and restart. Here, we show that during unperturbed replication, RTF2 regulates replisome localization of RNase H2, a heterotrimeric enzyme that removes RNA from RNA-DNA heteroduplexes. RTF2, like RNase H2, is essential for mammalian development and maintains normal replication speed. However, persistent RTF2 and RNase H2 at stalled replication forks prevent efficient replication restart, which is dependent on PRIM1, the primase component of DNA polymerase α-primase. Our data show a fundamental need for RTF2-dependent regulation of replication-coupled ribonucleotide removal and reveal the existence of PRIM1-mediated direct replication restart in mammalian cells.
Asunto(s)
Replicación del ADN , ADN , Animales , ADN/genética , ADN/metabolismo , Daño del ADN , Proteínas de Ciclo Celular/metabolismo , ARN/genética , Ribonucleasas/metabolismo , Mamíferos/genéticaRESUMEN
Genetic information is duplicated via the highly regulated process of DNA replication. The machinery coordinating this process, the replisome, encounters many challenges, including replication fork-stalling lesions that threaten the accurate and timely transmission of genetic information. Cells have multiple mechanisms to repair or bypass lesions that would otherwise compromise DNA replication1,2. We have previously shown that proteasome shuttle proteins, DNA Damage Inducible 1 and 2 (DDI1/2) function to regulate Replication Termination Factor 2 (RTF2) at the stalled replisome, allowing for replication fork stabilization and restart3. Here we show that RTF2 regulates replisome localization of RNase H2, a heterotrimeric enzyme responsible for removing RNA in the context of RNA-DNA heteroduplexes4-6. We show that during unperturbed DNA replication, RTF2, like RNase H2, is required to maintain normal replication fork speeds. However, persistent RTF2 and RNase H2 at stalled replication forks compromises the replication stress response, preventing efficient replication restart. Such restart is dependent on PRIM1, the primase component of DNA polymerase α-primase. Our data show a fundamental need for regulation of replication-coupled ribonucleotide incorporation during normal replication and the replication stress response that is achieved through RTF2. We also provide evidence for PRIM1 function in direct replication restart following replication stress in mammalian cells.
RESUMEN
Biomolecular condensates organize cellular functions in the absence of membranes. These membraneless organelles can form through liquid-liquid phase separation coalescing RNA and proteins into well-defined, yet dynamic, structures distinct from the surrounding cellular milieu. Numerous physiological and disease-causing processes link to biomolecular condensates, which could impact drug discovery in several ways. First, disruption of pathological condensates seeded by mutated proteins or RNAs may provide new opportunities to treat disease. Second, condensates may be leveraged to tackle difficult-to-drug targets lacking binding pockets whose function depends on phase separation. Third, condensate-resident small molecules and RNA therapeutics may display unexpected pharmacology. We discuss the potential impact of phase separation on drug discovery and RNA therapeutics, leveraging concrete examples, towards novel clinical opportunities.
Asunto(s)
Orgánulos , ARN , Condensados Biomoleculares , Descubrimiento de Drogas , Humanos , Orgánulos/química , Orgánulos/metabolismo , Proteínas/metabolismo , ARN/análisisRESUMEN
Severe cellular sensitivity and aberrant chromosomal rearrangements in response to DNA interstrand crosslink (ICL) inducing agents are hallmarks of Fanconi anemia (FA) deficient cells. These phenotypes have previously been ascribed to inappropriate activity of non-homologous end joining (NHEJ) rather than a direct consequence of DNA ICL repair defects. Here we used chemical inhibitors, RNAi, and Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)-Cas9 to inactivate various components of NHEJ in cells from FA patients. We show that suppression of DNA-PKcs, DNA Ligase IV, and 53BP1 is not capable of rescuing ICL-induced proliferation defects and only 53BP1 knockout partially suppresses the chromosomal abnormalities of FA patient cells.
Asunto(s)
Daño del ADN , Reparación del ADN por Unión de Extremidades , Anemia de Fanconi/metabolismo , Fibroblastos/metabolismo , Proteínas de Unión al Calcio/genética , Proteínas de Unión al Calcio/metabolismo , Línea Celular Transformada , Proliferación Celular , ADN Ligasa (ATP)/genética , ADN Ligasa (ATP)/metabolismo , Anemia de Fanconi/genética , Anemia de Fanconi/patología , Proteína del Grupo de Complementación A de la Anemia de Fanconi/genética , Fibroblastos/patología , Fibroblastos/efectos de la radiación , Células HCT116 , Humanos , Mutación , Proteína 1 de Unión al Supresor Tumoral P53/genética , Proteína 1 de Unión al Supresor Tumoral P53/metabolismoRESUMEN
The protection and efficient restart of stalled replication forks is critical for the maintenance of genome integrity. Here, we identify a regulatory pathway that promotes stalled forks recovery from replication stress. We show that the mammalian replisome component C20orf43/RTF2 (homologous to S. pombe Rtf2) must be removed for fork restart to be optimal. We further show that the proteasomal shuttle proteins DDI1 and DDI2 are required for RTF2 removal from stalled forks. Persistence of RTF2 at stalled forks results in fork restart defects, hyperactivation of the DNA damage signal, accumulation of single-stranded DNA (ssDNA), sensitivity to replication drugs, and chromosome instability. These results establish that RTF2 removal is a key determinant for the ability of cells to manage replication stress and maintain genome integrity.
Asunto(s)
Proteínas de Ciclo Celular/metabolismo , Daño del ADN/genética , Replicación del ADN/genética , Proteínas de Unión al ADN/metabolismo , ADN/genética , Inestabilidad Genómica/genética , Proteasas de Ácido Aspártico/genética , Ciclo Celular/genética , Proteínas de Ciclo Celular/genética , Línea Celular Tumoral , ADN/biosíntesis , Reparación del ADN/genética , ADN de Cadena Simple/metabolismo , Proteínas de Unión al ADN/genética , Células HeLa , Humanos , Interferencia de ARN , ARN Interferente Pequeño/genética , Origen de Réplica/genética , Estrés Fisiológico/genéticaRESUMEN
Deficiency of FANCD2/FANCI-associated nuclease 1 (FAN1) in humans leads to karyomegalic interstitial nephritis (KIN), a rare hereditary kidney disease characterized by chronic renal fibrosis, tubular degeneration, and characteristic polyploid nuclei in multiple tissues. The mechanism of how FAN1 protects cells is largely unknown but is thought to involve FAN1's function in DNA interstrand cross-link (ICL) repair. Here, we describe a Fan1-deficient mouse and show that FAN1 is required for cellular and organismal resistance to ICLs. We show that the ubiquitin-binding zinc finger (UBZ) domain of FAN1, which is needed for interaction with FANCD2, is not required for the initial rapid recruitment of FAN1 to ICLs or for its role in DNA ICL resistance. Epistasis analyses reveal that FAN1 has cross-link repair activities that are independent of the Fanconi anemia proteins and that this activity is redundant with the 5'-3' exonuclease SNM1A. Karyomegaly becomes prominent in kidneys and livers of Fan1-deficient mice with age, and mice develop liver dysfunction. Treatment of Fan1-deficient mice with ICL-inducing agents results in pronounced thymic and bone marrow hypocellularity and the disappearance of c-kit(+) cells. Our results provide insight into the mechanism of FAN1 in ICL repair and demonstrate that the Fan1 mouse model effectively recapitulates the pathological features of human FAN1 deficiency.
Asunto(s)
Endodesoxirribonucleasas/deficiencia , Endodesoxirribonucleasas/genética , Riñón/patología , Hepatopatías/genética , Animales , Médula Ósea/efectos de los fármacos , Reactivos de Enlaces Cruzados/farmacología , Daño del ADN/genética , Reparación del ADN/genética , Proteínas de Unión al ADN/metabolismo , Modelos Animales de Enfermedad , Endodesoxirribonucleasas/metabolismo , Endonucleasas/metabolismo , Epistasis Genética , Exodesoxirribonucleasas/metabolismo , Hígado/patología , Ratones , Enzimas Multifuncionales , Estructura Terciaria de Proteína , Transporte de ProteínasRESUMEN
Repair of DNA interstrand crosslinks requires action of multiple DNA repair pathways, including homologous recombination. Here, we report a de novo heterozygous T131P mutation in RAD51/FANCR, the key recombinase essential for homologous recombination, in a patient with Fanconi anemia-like phenotype. In vitro, RAD51-T131P displays DNA-independent ATPase activity, no DNA pairing capacity, and a co-dominant-negative effect on RAD51 recombinase function. However, the patient cells are homologous recombination proficient due to the low ratio of mutant to wild-type RAD51 in cells. Instead, patient cells are sensitive to crosslinking agents and display hyperphosphorylation of Replication Protein A due to increased activity of DNA2 and WRN at the DNA interstrand crosslinks. Thus, proper RAD51 function is important during DNA interstrand crosslink repair outside of homologous recombination. Our study provides a molecular basis for how RAD51 and its associated factors may operate in a homologous recombination-independent manner to maintain genomic integrity.
Asunto(s)
Reparación del ADN , ADN/metabolismo , Anemia de Fanconi/genética , Recombinasa Rad51/genética , Recombinasa Rad51/metabolismo , Proteína de Replicación A/metabolismo , Supervivencia Celular , Reactivos de Enlaces Cruzados , ADN Helicasas/metabolismo , Exodesoxirribonucleasas/metabolismo , Anemia de Fanconi/metabolismo , Femenino , Inestabilidad Genómica , Células HEK293 , Heterocigoto , Humanos , Lactante , Mutación , RecQ Helicasas/metabolismo , Helicasa del Síndrome de WernerRESUMEN
Alzheimer's disease (AD) is characterized by accumulation of the ß-amyloid peptide (Aß), which likely contributes to disease via multiple mechanisms. Increasing evidence implicates inflammation in AD, the origins of which are not completely understood. We investigated whether circulating Aß could initiate inflammation in AD via the plasma contact activation system. This proteolytic cascade is triggered by the activation of the plasma protein factor XII (FXII) and leads to kallikrein-mediated cleavage of high molecular-weight kininogen (HK) and release of proinflammatory bradykinin. Aß has been shown to promote FXII-dependent cleavage of HK in vitro. In addition, increased cleavage of HK has been found in the cerebrospinal fluid of patients with AD. Here, we show increased activation of FXII, kallikrein activity, and HK cleavage in AD patient plasma. Increased contact system activation is also observed in AD mouse model plasma and in plasma from wild-type mice i.v. injected with Aß42. Our results demonstrate that Aß42-mediated contact system activation can occur in the AD circulation and suggest new pathogenic mechanisms, diagnostic tests, and therapies for AD.
Asunto(s)
Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Factor XII/metabolismo , Factor XIIa/metabolismo , Anciano , Anciano de 80 o más Años , Péptidos beta-Amiloides/metabolismo , Animales , Biomarcadores/metabolismo , Estudios de Casos y Controles , Demencia/genética , Demencia/metabolismo , Modelos Animales de Enfermedad , Progresión de la Enfermedad , Factor XII/genética , Factor XIIa/genética , Femenino , Humanos , Inflamación , Calicreínas/sangre , Quininógenos/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Microscopía Electrónica de Transmisión , Fragmentos de Péptidos/metabolismo , Transferrina/metabolismoRESUMEN
UNLABELLED: Carcinoma-associated fibroblasts (CAFs) are now widely appreciated for their contributions to tumor progression. However, the ability of CAFs to regulate anoikis, detachment-induced cell death, has yet to be investigated. Here, a new role for CAFs in blocking anoikis in multiple cell lines, facilitating luminal filling in three-dimensional cell culture, and promoting anchorage-independent growth is defined. In addition, a novel mechanism underlying anoikis inhibition is discovered. Importantly, it was demonstrated that CAFs secrete elevated quantities of insulin-like growth factor-binding proteins (IGFBPs) that are both necessary for CAF-mediated anoikis inhibition and sufficient to block anoikis in the absence of CAFs. Furthermore, these data reveal a unique antiapoptotic mechanism for IGFBPs: the stabilization of the antiapoptotic protein Mcl-1. In aggregate, these data delineate a novel role for CAFs in promoting cell survival during detachment and unveil an additional mechanism by which the tumor microenvironment contributes to cancer progression. These results also identify IGFBPs as potential targets for the development of novel chemotherapeutics designed to eliminate detached cancer cells. IMPLICATIONS: The ability of CAF-secreted IGFBPs to block anoikis in breast cancer represents a novel target for the development of therapeutics aimed at specifically eliminating extracellular matrix-detached breast cancer cells.