Using an approach known as RNA interference, we have specifically depleted human cells of the FANCJ DNA helicase and characterized the sensitivity of the cells to a small molecule compound that stabilizes G-quadruplex DNA structures. This work enabled us to elucidate a novel function of the FANCJ helicase in the manintenace of chromosomal stability. Since individuals carrying homozygous mutations in the FANCJ helicase gene have a genetic disorder known as Fanconi Anemia characterized by genomic instability and cancer, we believe our results shed new insights to the cellular pathways of FANCJ that serve to counter replciational stress due to alterante DNA structures such as G-quadruplexes that arise in vivo. We have used isogenic pairs of mutant and corrected chicken DT40 cells as well as human cells for genetic complementation studies. The mutant cell lines were used for structure-function studies of patient derived helicase-inactivating mutations. This work enabled us to define genotype-phenotype relationships between clinically relevant mutations and human genetic diseases. Another aspect of this work was to used genetically defined cancer and normal cell lines and small molecules to probed the molecualr and cellular functions of the Werner syndrome helicase. These efforts enabled us to determine that inhibition of WRN helicase activity inhibits cell proliferation and its DNA repair function in vivo. These efforts in the basic sciences help to advance the idea that DNA repair proteins may be targeted in anti-cancer therapy to increase the sensitivity of tumors to DNA damaging chemotherapy drugs or radiation. We have also employed yeast as a model genetic system to study the role of the Werner syndrome helicase in DNA replciation and repair. This work has enabled us to characterize the catalytic requirements of WRN in a defined genetic DNA repair pathway that operates to provide cellular resistance to alkylating agents which impose replicational stress. Lastly, we have utilized mouse as a model genetic system to characterize the role of a helicase ortholog (RECQ1) found in humans whose biological significance is not well understood. Characterization of th eprimary mouse embryonic fibroblasts from RECQ1 knockout mice has revealed that the RECQ1 helicase has unique and important roles in genomic stability maintenance.

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Calì, Federica; Bharti, Sanjay Kumar; Di Perna, Roberta et al. (2016) Tim/Timeless, a member of the replication fork protection complex, operates with the Warsaw breakage syndrome DNA helicase DDX11 in the same fork recovery pathway. Nucleic Acids Res 44:705-17
Marchese, Francesco P; Grossi, Elena; Marín-Béjar, Oskar et al. (2016) A Long Noncoding RNA Regulates Sister Chromatid Cohesion. Mol Cell 63:397-407
Banerjee, Taraswi; Aggarwal, Monika; Sommers, Joshua A et al. (2016) Biochemical and cell biological assays to identify and characterize DNA helicase inhibitors. Methods 108:130-41
Banerjee, Taraswi; Brosh Jr, Robert M (2015) RECQL: a new breast cancer susceptibility gene. Cell Cycle :0
Sommers, Joshua A; Suhasini, Avvaru N; Brosh Jr, Robert M (2015) Protein degradation pathways regulate the functions of helicases in the DNA damage response and maintenance of genomic stability. Biomolecules 5:590-616
Banerjee, Taraswi; Sommers, Joshua A; Huang, Jing et al. (2015) Catalytic strand separation by RECQ1 is required for RPA-mediated response to replication stress. Curr Biol 25:2830-8
Bharti, Sanjay Kumar; Khan, Irfan; Banerjee, Taraswi et al. (2014) Molecular functions and cellular roles of the ChlR1 (DDX11) helicase defective in the rare cohesinopathy Warsaw breakage syndrome. Cell Mol Life Sci 71:2625-39
Henderson, Alexander; Wu, Yuliang; Huang, Yu Chuan et al. (2014) Detection of G-quadruplex DNA in mammalian cells. Nucleic Acids Res 42:860-9
Cantor, Sharon B; Brosh Jr, Robert M (2014) What is wrong with Fanconi anemia cells? Cell Cycle 13:3823-7
Brosh Jr, Robert M; Cantor, Sharon B (2014) Molecular and cellular functions of the FANCJ DNA helicase defective in cancer and in Fanconi anemia. Front Genet 5:372

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