The Fanconi anemia (FA) phenotype on a cellular level is marked by genomic instability and hypersensitivity to DNA damage. FA proteins participate in complexes that juxtapose the FA pathway with other more defined pathways involved in cellular response to DNA damage, such as ATR, BRCA1, and RAD51. Recent work has served to shift focus of FA biology and the normal functions of these proteins onto homologous recombination pathways. However, much remains to be ascertained in normal FA biochemistry or about the manner in which FA proteins contribute to hematopoiesis and leukemia, as the FA proteins contain few known functional motifs. Insight into the biochemical pathway of FA is important because this would lead to a mechanism whereby genomic instability occurs, which is a basic cause of cancer. This understanding makes possible interventions for cancer prevention as well as manipulation of genomic instability for cancer therapy. The long-term goal of my laboratory is to define mechanisms of genomic instability, using FA as a model, as well as to understand the normal function of FA proteins. The central hypothesis for the proposed research is that FANCD2 acts as a signal transduction protein to interact with downstream effectors such as the MSH2, the mismatch repair protein, and the MCM2-7 complex, which is critical for pre-origin loading of the replication machinery. Our work suggests that both these processes depend on upstream phosphorylation events. To test our central hypothesis and carry out this application, we will pursue the following specific aims:
Aim #1 : Determine the functional consequence of FANCD2-MSH2 interaction The working hypothesis for Aim #1 is that FANCD2-MSH2 interaction is important for the normal DNA damage response. Our data have shown that not only does MSH2 knockdown result in DNA damage hypersensitivity but also double knockdown of both FANCD2 and MSH2 contradictorily results in cellular resistance.
Aim #2 : Determine the functional consequence of FANCD2-MLH1 interaction The working hypothesis for Aim #2 is that FANCD2-MLH1 interaction is important for the normal DNA damage response. We show that MLH1 loss does not affect FANCD2 monoubiquitylation but does prevent the propagation of signal to chromatin and subsequent increased sensitivity to DNA crosslinkers.
Aim #3 : Demonstrate the functional consequence of FANCD2-MCM2-7 interaction The working hypothesis for Aim #2 is that FANCD2-MCM2-7 interaction regulates the assembly of the replication complex at the origin by responding to DNA damage during S phase. Our data indicate that binding to a subset of the MCM subunits results in inhibition of replication complex assembly. Understanding the FA pathway will further elaborate a key repair pathway as well as lend insight into avenues of targeting cancer therapy.

Public Health Relevance

Fanconi anemia (FA) is a genetic disease of cancer susceptibility whose dissection has led to the study of the DNA damage response and homologous recombinatorial repair. We have found that the central protein FANCD2 in the FA pathway interacts with the mismatch repair pathway via MSH2 and MLH1 as well the replicative helicase MCM2-7. We hypothesize that FANCD2 regulates the action of repair and replication through these proteins. Study of these pathways will allow us to not only understand basic mechanisms of DNA repair and response but also will uncover avenues whereby mechanisms of cancer and response to cancer therapy may be modulated.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
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Molecular and Cellular Hematology (MCH)
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Qasba, Pankaj
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Yale University
Schools of Medicine
New Haven
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Longerich, Simonne; Kwon, Youngho; Tsai, Miaw-Sheue et al. (2014) Regulation of FANCD2 and FANCI monoubiquitination by their interaction and by DNA. Nucleic Acids Res 42:5657-70
Chen, Xiaoyong; Wilson, James B; McChesney, Patricia et al. (2014) The Fanconi anemia proteins FANCD2 and FANCJ interact and regulate each other's chromatin localization. J Biol Chem 289:25774-82
Chirnomas, S Deborah; Kupfer, Gary M (2013) The inherited bone marrow failure syndromes. Pediatr Clin North Am 60:1291-310
Kupfer, Gary M (2013) Fanconi anemia: a signal transduction and DNA repair pathway. Yale J Biol Med 86:491-7
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Zhi, Gang; Chen, Xiaoyong; Newcomb, William et al. (2010) Purification of FANCD2 sub-complexes. Br J Haematol 150:88-92
Wilson, James B; Blom, Eric; Cunningham, Ryan et al. (2010) Several tetratricopeptide repeat (TPR) motifs of FANCG are required for assembly of the BRCA2/D1-D2-G-X3 complex, FANCD2 monoubiquitylation and phleomycin resistance. Mutat Res 689:12-20
Song, Ihn Young; Palle, Komaraiah; Gurkar, Aditi et al. (2010) Rad18-mediated translesion synthesis of bulky DNA adducts is coupled to activation of the Fanconi anemia DNA repair pathway. J Biol Chem 285:31525-36
Zhi, Gang; Wilson, James B; Chen, Xiaoyong et al. (2009) Fanconi anemia complementation group FANCD2 protein serine 331 phosphorylation is important for fanconi anemia pathway function and BRCA2 interaction. Cancer Res 69:8775-83

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