ABSTRACT
Although DNA interstrand crosslinking (ICL) agents such as mitomycin C, cisplatin and psoralen serve as potent anticancer drugs, these agents are known to have dose-limiting toxic effects on normal cells. Moreover, tumor resistance to these agents has been reported. Here, we show that trans-dichlorooxovanadium (IV) complex of pyrenyl terpyridine (VDC) is a novel photoinducible DNA crosslinking agent. By a combination of in vitro and ex vivo experiments including plasmid-based assays, we find that VDC forms monoadducts on the DNA and can be activated by UV-A and visible light to generate DNA interstrand crosslinks. VDC efficiently activates Fanconi anemia (FA) pathway of DNA interstrand crosslink repair. Strikingly, photoinduction of VDC induces prolonged activation of cell cycle checkpoint and a high degree of cell death in homologous recombination (HR)/ICL repair defective cells. Moreover, VDC specifically targets cells that express pathological RAD51C mutants. These data imply that VDC can be potentially used for cancer therapy and suggest that tumors arising in patients with gene mutations in FA and HR repair pathway can be specifically targeted by a photoactivatable VDC.
Subject(s)
Antineoplastic Agents/pharmacology , Coordination Complexes/pharmacokinetics , DNA Damage/drug effects , DNA Repair/drug effects , Neoplasms/pathology , Photosensitizing Agents/pharmacology , Blotting, Western , Cell Line, Tumor , Cell Survival/drug effects , Comet Assay , Cross-Linking Reagents/pharmacology , DNA Adducts/drug effects , Fluorescent Antibody Technique , Humans , Neoplasms/geneticsABSTRACT
Mammalian RAD51 paralogs are implicated in the repair of collapsed replication forks by homologous recombination. However, their physiological roles in replication fork maintenance prior to fork collapse remain obscure. Here, we report on the role of RAD51 paralogs in short-term replicative stress devoid of DSBs. We show that RAD51 paralogs localize to nascent DNA and common fragile sites upon replication fork stalling. Strikingly, RAD51 paralogs deficient cells exhibit elevated levels of 53BP1 nuclear bodies and increased DSB formation, the latter being attributed to extensive degradation of nascent DNA at stalled forks. RAD51C and XRCC3 promote the restart of stalled replication in an ATP hydrolysis dependent manner by disengaging RAD51 and other RAD51 paralogs from the halted forks. Notably, we find that Fanconi anemia (FA)-like disorder and breast and ovarian cancer patient derived mutations of RAD51C fails to protect replication fork, exhibit under-replicated genomic regions and elevated micro-nucleation. Taken together, RAD51 paralogs prevent degradation of stalled forks and promote the restart of halted replication to avoid replication fork collapse, thereby maintaining genomic integrity and suppressing tumorigenesis.
Subject(s)
DNA Replication , DNA-Binding Proteins/physiology , DNA/metabolism , Amino Acid Motifs , Animals , Breast Neoplasms/genetics , Cell Line , Chromatin/metabolism , Chromosome Fragile Sites , Cricetinae , Cricetulus , DNA Breaks , DNA, Single-Stranded/metabolism , DNA-Binding Proteins/chemistry , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , DNA-Directed DNA Polymerase , Fanconi Anemia Complementation Group Proteins/metabolism , Female , HeLa Cells , Humans , Multienzyme Complexes , Mutation , Ovarian Neoplasms/genetics , S PhaseABSTRACT
Scrub typhus and leptospirosis are both zoonosis and systemic febrile illnesses with diverse clinical manifestations and they may present with similar signs and symptoms. We present a case of co-infection of scrub typhus and leptospirosis from Himachal Pradesh in the Himalayan region of India.
Subject(s)
Antibodies, Bacterial/blood , Coinfection/diagnosis , Leptospira/immunology , Leptospirosis/complications , Orientia tsutsugamushi/immunology , Scrub Typhus/complications , Adult , Coinfection/microbiology , Female , Humans , Immunoglobulin M/blood , India , Leptospirosis/diagnosis , Leptospirosis/microbiology , Scrub Typhus/diagnosis , Scrub Typhus/microbiologyABSTRACT
Scrub typhus, a zoonosis, is a systemic febrile illness with diverse clinical manifestations. It may also present with signs and symptoms of acute abdomen. We present two serologically confirmed cases of scrub typhus presenting with acute abdomen that were managed conservatively with antibiotics.
