Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0002871 (anemia)
 52,094 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fanconi anemia (FA) is a multigenic autosomal recessive cancer susceptibility syndrome. The FA pathway regulates the monoubiquitination of FANCD2 and the assembly of damage-associated FANCD2 nuclear foci. How FANCD2 monoubiquitination is coupled to the DNA-damage response has remained undetermined. Here, we demonstrate that the ATR checkpoint kinase and RPA1 are required for efficient FANCD2 monoubiquitination. Deficiency of ATR function, either in Seckel syndrome, which clinically resembles Fanconi anemia, or by siRNA silencing, results in the formation of radial chromosomes in response to the DNA cross-linker, mitomycin C (MMC), thus mimicking the chromosome instability of FA cells.
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PMID:ATR couples FANCD2 monoubiquitination to the DNA-damage response. 1531 22

The Fanconi anemia (FA) pathway is a DNA damage-activated signaling pathway which regulates cellular resistance to DNA cross-linking agents. Cloned FA genes and proteins cooperate in this pathway, and monoubiquitination of FANCD2 is a critical downstream event. The cell cycle checkpoint kinase ATR is required for the efficient monoubiquitination of FANCD2, while another checkpoint kinase, ATM, directly phosphorylates FANCD2 and controls the ionizing radiation (IR)-inducible intra-S-phase checkpoint. In the present study, we identify two novel DNA damage-inducible phosphorylation sites on FANCD2, threonine 691 and serine 717. ATR phosphorylates FANCD2 on these two sites, thereby promoting FANCD2 monoubiquitination and enhancing cellular resistance to DNA cross-linking agents. Phosphorylation of the sites is required for establishment of the intra-S-phase checkpoint response. IR-inducible phosphorylation of threonine 691 and serine 717 is also dependent on ATM and is more strongly impaired when both ATM and ATR are knocked down. Threonine 691 is phosphorylated during normal S-phase progression in an ATM-dependent manner. These findings further support the functional connection of ATM/ATR kinases and FANCD2 in the DNA damage response and support a role for the FA pathway in the coordination of the S phase of the cell cycle.
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PMID:Phosphorylation of FANCD2 on two novel sites is required for mitomycin C resistance. 1694 40

The eleven Fanconi anemia (FA) proteins cooperate in a novel pathway required for the repair of DNA cross-links. Eight of the FA proteins (A, B, C, E, F, G, L, and M) form a core enzyme complex, required for the monoubiquitination of FANCD2 and the assembly of FANCD2 nuclear foci. Here, we show that, in response to DNA damage, Chk1 directly phosphorylates the FANCE subunit of the FA core complex on two conserved sites (threonine 346 and serine 374). Phosphorylated FANCE assembles in nuclear foci and colocalizes with FANCD2. A nonphosphorylated mutant form of FANCE (FANCE-T346A/S374A), when expressed in a FANCE-deficient cell line, allows FANCD2 monoubiquitination, FANCD2 foci assembly, and normal S-phase progression. However, the mutant FANCE protein fails to complement the mitomycin C hypersensitivity of the transfected cells. Taken together, these results elucidate a novel role of Chk1 in the regulation of the FA/BRCA pathway and in DNA cross-link repair. Chk1-mediated phosphorylation of FANCE is required for a function independent of FANCD2 monoubiquitination.
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PMID:Chk1-mediated phosphorylation of FANCE is required for the Fanconi anemia/BRCA pathway. 1729 36

Here, we show that the human homologue of the Caenorhabditis elegans biological clock protein CLK-2 (HCLK2) associates with the S-phase checkpoint components ATR, ATRIP, claspin and Chk1. Consistent with a critical role in the S-phase checkpoint, HCLK2-depleted cells accumulate spontaneous DNA damage in S-phase, exhibit radio-resistant DNA synthesis, are impaired for damage-induced monoubiquitination of FANCD2 and fail to recruit FANCD2 and Rad51 (critical components of the Fanconi anaemia and homologous recombination pathways, respectively) to sites of replication stress. Although Thr 68 phosphorylation of the checkpoint effector kinase Chk2 remains intact in the absence of HCLK2, claspin phosphorylation and degradation of the checkpoint phosphatase Cdc25A are compromised following replication stress as a result of accelerated Chk1 degradation. ATR phosphorylation is known to both activate Chk1 and target it for proteolytic degradation, and depleting ATR or mutation of Chk1 at Ser 345 restored Chk1 protein levels in HCLK2-depleted cells. We conclude that HCLK2 promotes activation of the S-phase checkpoint and downstream repair responses by preventing unscheduled Chk1 degradation by the proteasome.
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PMID:HCLK2 is essential for the mammalian S-phase checkpoint and impacts on Chk1 stability. 1738 38

Chk1 is a conserved kinase that imposes cell cycle delays in response to impediments to DNA replication. Recent experiments have further defined effects of Chk1 on the activity of mammalian origins of DNA replication and progression of replication forks. Moreover, Chk1 now appears to help defend genomic integrity through effects on several other pathways, including Fanconi anemia proteins, the mitotic spindle, and transcription of cell cycle-related genes. These findings can account for the requirement for Chk1 in normal proliferating cells of the early embryo and suggest the potential for diverse effects of Chk1 inhibition in cancer therapy.
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PMID:Expanded roles for Chk1 in genome maintenance. 1842 30

The Fanconi anemia (FA) pathway is implicated in DNA repair and cancer predisposition. Central to this pathway is the FA core complex, which is targeted to chromatin by FANCM and FAAP24 following replication stress. Here we show that FANCM and FAAP24 interact with the checkpoint protein HCLK2 independently of the FA core complex. In addition to defects in FA pathway activation, downregulation of FANCM or FAAP24 also compromises ATR/Chk1-mediated checkpoint signaling, leading to defective Chk1, p53, and FANCE phosphorylation; 53BP1 focus formation; and Cdc25A degradation. As a result, FANCM and FAAP24 deficiency results in increased endogenous DNA damage and a failure to efficiently invoke cell-cycle checkpoint responses. Moreover, we find that the DNA translocase activity of FANCM, which is dispensable for FA pathway activation, is required for its role in ATR/Chk1 signaling. Our data suggest that DNA damage recognition and remodeling activities of FANCM and FAAP24 cooperate with ATR/Chk1 to promote efficient activation of DNA damage checkpoints.
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PMID:FANCM and FAAP24 function in ATR-mediated checkpoint signaling independently of the Fanconi anemia core complex. 1899 30

Cell division cycle 5-like protein (Cdc5L) is a core component of the putative E3 ubiquitin ligase complex containing Prp19/Pso4, Plrg1 and Spf27. This complex has been shown to have a role in pre-messenger RNA splicing from yeast to humans; however, more recent studies have described a function for this complex in the cellular response to DNA damage. Here, we show that Cdc5L interacts physically with the cell-cycle checkpoint kinase ataxia-telangiectasia and Rad3-related (ATR). Depletion of Cdc5L by RNA-mediated interference methods results in a defective S-phase cell-cycle checkpoint and cellular sensitivity in response to replication-fork blocking agents. Furthermore, we show that Cdc5L is required for the activation of downstream effectors or mediators of ATR checkpoint function such as checkpoint kinase 1 (Chk1), cell cycle checkpoint protein Rad 17 (Rad17) and Fanconi anaemia complementation group D2 protein (FancD2). In addition, we have mapped the ATR-binding region in Cdc5L and show that a deletion mutant that is unable to interact with ATR is defective in the rescue of the checkpoint deficiency in Cdc5L-depleted cells. These findings show a new function for Cdc5L in the regulation of the ATR-mediated cell-cycle checkpoint in response to genotoxic agents.
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PMID:Cdc5L interacts with ATR and is required for the S-phase cell-cycle checkpoint. 1963 97

DNA interstrand crosslinks (ICLs) are the most toxic lesions induced by chemotherapeutic agents such as mitomycin C and cisplatin. By covalently linking both DNA strands, ICLs prevent DNA melting, transcription, and replication. Studies on ICL signaling and repair have been limited, because these drugs generate additional DNA lesions that trigger checkpoint signaling. Here, we monitor sensing, signaling from, and repairing of a single site-specific ICL in cell-free extract derived from Xenopus eggs and in mammalian cells. Notably, we demonstrate that ICLs trigger a checkpoint response independently of origin-initiated DNA replication and uncoupling of DNA polymerase and DNA helicase. The Fanconi anemia pathway acts upstream of RPA-ATR-Chk1 to generate the ICL signal. The system also repairs ICLs in a reaction that involves extensive, error-free DNA synthesis. Repair occurs by both origin-dependent and origin-independent mechanisms. Our data suggest that cell sensitivity to crosslinking agents results from both checkpoint and DNA repair defects.
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PMID:Checkpoint signaling from a single DNA interstrand crosslink. 1974 63

Human p29 is a chromatin-associated protein and the silencing of p29 expression increases cell population in G(1) phase and decreases phosphorylation levels of Chk1 and Chk2 in response to UV treatment. To further characterize the function of p29, U2OS and Fanconi anemia complementation group G (FA-G) cells with constitutive p29 expression have been established. Analyses of these cells identified increased phosphorylation levels of Chk1 and Chk2, which were accompanied by elevated amounts of chromatin-associated Mre11-Rad50-Nbs1 complex and ATR-IP. Monoubiquitination of the FA ID complex was restored in p29 stably expressing FA-G cells. Moreover, lower tumor incidence was observed in mp29 transgenic mice after UV irradiation. These results suggest the involvement of p29 in the DNA damage responses and Fanconi anemia pathway.
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PMID:Involvement of p29 in DNA damage responses and Fanconi anemia pathway. 1974 26

Fanconi anemia is a cancer-prone inherited bone marrow failure and cancer susceptibility syndrome with at least 13 complementation groups (FANCA, FANCB, FANCC, FANCD1, FANCD2, FANCE, FANCF, FANCG, FANCI, FANCJ, FANCL, FANCM, and FANCN). Our laboratory has previously described several regulatory phosphorylation events for core complex member proteins FANCG and FANCA by phosphorylation. In this study, we report a novel phosphorylation site serine 331 (S331) of FANCD2, the pivotal downstream player of the Fanconi anemia pathway. Phosphorylation of S331 is important for its DNA damage-inducible monoubiquitylation, resistance to DNA cross-linkers, and in vivo interaction with FANCD1/BRCA2. A phosphomimetic mutation at S331 restores all of these phenotypes to wild-type. In vitro and in vivo experiments show that phosphorylation of S331 is mediated by CHK1, the S-phase checkpoint kinase implicated in the Fanconi anemia DNA repair pathway.
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PMID:Fanconi anemia complementation group FANCD2 protein serine 331 phosphorylation is important for fanconi anemia pathway function and BRCA2 interaction. 1986 35


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