Pharmacological Sciences - Orlando Schärer, PhD

Orlando Schärer, PhD - Associate Professor

Chemical Biology of Mammalian DNA Repair

Orlando D. Schärer, PhD

Associate Professor, Pharmacological Sciences
Graduate Chemistry Building Room 619
SUNY Stony Brook
Stony Brook, NY 11794-3400
Phone: 631-632-7545
Fax: 631-632-7546
E-mail: orlando@pharm.stonybrook.edu
Ph.D., Harvard University
Postdoctoral, Erasmus University, Rotterdam, The Netherlands
Schärer lab page

Research
Our work combines organic chemistry, biochemistry, and molecular and cellular biology to investigate the mechanisms of DNA repair in higher eukaryotes and the relationship of these processes to anti-tumor and gene therapy.

One area of interest in our laboratory is human nucleotide excision repair (NER), a pathway in which 30 proteins cooperate to excise lesions from DNA. Defects in NER are associated with the hereditary syndrome Xeroderma pigmentosum, which is characterized by extreme UV sensitivity and a more than 2000-fold increase in cancer incidence. We have generated photoreactive and fluorescent NER substrates that we are using to study how the different NER proteins recognize damaged sites in DNA. We have characterized the mechanisms of substrate binding and catalysis of ERCC1-XPF and XPG, the two endonucleases in NER and are studying how their activity is regulated in a multi-protein complex by other NER proteins. One area of particular present interest is the study of how the various steps in NER are coordinated, ensuring that only damaged DNA is processed without the formation of potentially mutagenic or recombinogenic intermediates.

Our interest in the study of interstrand crosslink (ICL) repair, which is only poorly understood in humans, stems from the importance of ICLs as lesions formed by agents used in chemotherapy. We have developed two new methods for the synthesis of ICLs, thereby removing one important obstacle in the study of ICL repair, the synthesis of defined site-specific ICLs. We have designed a reporter assay to study ICL repair in living cells to delineate the genetic requirement of various ICL repair pathways. These studies will provide the basis for the biochemical investigation of human ICL repair pathways.

In our final effort we aim to discover new chemistry that might be used to induce single base changes in genomic DNA. As a first step toward this goal we have generated oligonucleotides containing a modified base capable of a functional group transfer reaction that can effect the covalent modification of base opposite to it. We are testing and expanding the scope of this reaction and are investigating its usefulness in inducing substitutions at specific sites in reporter genes in living cells. The successful development of this technology would be invaluable for functional genomics and gene therapy.

Selected Publications

Staresincic L, Enzlin JH, Gourdin AM, Wijgers N, Dunand-Sauthier I, Giglia-Mari G, Clarkson SG, Vermuelen W, Schärer OD (2007) Coordination of Dual Incision and Repair Synthesis in Human Nucleotide Excision Repair. Submitted

Tsodikov OV, Ivanov D, Orelli B, Staresincic L, Shoshani I, Schärer OD, Wagner G, Ellenberger T (2007) Structural Basis for the Recruitment of ERCC1-XPF to Nucleotide Excision Repair Complexes by XPA. Submitted

Schärer OD (2007) Molecular basis for different disease states caused by mutations in TFIIH and XPG (Hot topics in DNA repair article). Submitted

Schärer OD (2007) XPG: its product and biological roles. In Molecular Mechanisms of Xeroderma Pigmentosum (Ahmad SI and Hanaoka F, eds) Landes Biosciences, in press

Hohl M, Dunand-Sauthier I, Staresincic L, Jacquier-Gubler P, Thorel F, Clarkson SG, Schärer OD (2007) Domain swapping between FEN-1 and XPG identifies regions in XPG that mediate NER activity and substrate specificity. Nucl Acids Res, 35, 3053-3063

Maltseva E, Rechkunova N, Gillet LCJ, Petruseva I, Schärer OD; Olga I. Lavrik OI (2007) Crosslinking of the NER damage recognition proteins XPC-HR23B, XPA and RPA to photoreactive probes that mimic DNA damages. Biochem Biophys Acta, 1770, 781-789

Alzeer J, Schärer OD (2006) A modified thymine residue for the synthesis of site-specific DNA interstrand crosslinks. Nucl Acids Res, 34, 4458-4466

Gillet LCJ, Schärer OD (2006) Molecular mechanisms underlying mammalian nucleotide excision repair (Invited Review). Chem Rev 106, 253-276

Tsodikov OV, Enzlin, JH, Schärer, OD, Ellenberger T (2005) Crystal structure and DNA binding functions of ERCC1, a subunit of the DNA structure-specific endonuclease XPF-ERCC1. Proc Natl Acad Sci USA 102, 11236-11241

Gillet LCJ, Alzeer J, Schärer OD (2005) Site-specific incorporation of N-(deoxyguanosin-8-yl)-2-acetylaminofluorene (dG-AAF) into oligonucleotides using modified “ultra-mild” DNA synthesis. Nucl Acids Res 33, 1961-1969

Schärer OD (2005) DNA Interstand Crosslinks: Natural and drug-induced DNA adducts that induce unique cellular responses (Review). ChemBioChem 6, 27-32

Schärer, O. and Schultz, C. (2005) Closing the Gap between Chemistry and Biology (Editorial). ChemBioChem 6, 1-3

Dunand-Sauthier I, Hohl M, Thorel F, Jaquier-Gubler P, Clarkson SG, Schärer OD (2005) The spacer region in XPG mediates recruitment to nucleotide excision repair complexes and determines substrate specificity. J Biol Chem 280, 7030-7037

Tapias A, Auriol J, Forget D, Enzlin JH, Schärer OD, Coin F, Coulombe B, Egly JM (2004) Ordered conformational changes in damaged DNA induced by nucleotide excision repair factors. J Biol Chem 279, 19074-19083

Schärer OD (2003) Chemistry and biology of mammalian DNA repair (Invited Review). Angew Chem Int Edit 42, 2946-2974

Hohl M, Thorel F, Clarkson SG, Schärer OD (2003) Defining the structural determinants of XPG binding to ss/dsDNA junctions. J Biol Chem 278, 19500-19508

Gillet LCJ, Schärer OD (2002) Preparation of C8-Amine and Acetylamine Adducts of 2’-Deoxyguanosine Suitably Protected for DNA Synthesis. Org Lett 4, 4205-4208

Enzlin JH, Schärer OD (2002) Identification of the active site of the nucleotide excision repair endonuclease XPF-ERCC1 reveals a highly conserved nuclease motif. EMBO J 21, 2045-2053

Last Updated ( Wednesday, 15 August 2007 )

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