University of Pittsburgh Cancer Institute (UPCI)

Genome Stability

ERCC1Genomic instability is a major cause of tumor formation. During cell division, genomic instability is minimized by high-fidelity DNA replication in S-phase, precise chromosome segregation in mitosis, error-free repair of sporadic DNA damage, and coordinated cell cycle progression. Alterations in these processes can cause cellular senescence and premature aging or tumor formation.

Selected Publications

  • How human DNA repair proteins survey the genome for UV-induced photoproducts remains a poorly understood aspect of the initial damage recognition step in nucleotide excision repair (NER). Single molecule experiments revealed that the human UV-damaged DNA-binding protein (UV-DDB) performs a 3D search mechanism and displays a remarkable heterogeneity in the kinetics of damage recognition. Results indicate that UV-DDB examines sites on DNA in discrete steps before forming long-lived, nonmotile UV-DDB dimers (DDB1-DDB2)2 at sites of damage. These intermediate states are believed to represent discrete UV-DDB conformers on the trajectory to stable damage detection. (Ghodke et. al., Proc Natl Acad Sci U S A. 2014 May 6;111(18):E1862-71.)
  • Human telomeres are maintained by the shelterin protein complex in which TRF1 and TRF2 bind directly to duplex telomeric DNA. MCCBP investigators use single-molecule fluorescence imaging of quantum dot-labeled TRF1 and TRF2 to study how these proteins locate TTAGGG repeats on DNA tightropes. By virtue of its basic domain, TRF2 performs an extensive 1D search on nontelomeric DNA, whereas TRF1's 1D search is limited. Unlike the stable and static associations observed for other proteins at specific binding sites, TRF proteins possess reduced binding stability marked by transient binding and slow 1D diffusion on specific telomeric regions. These slow diffusion constants yield activation energy barriers to sliding ~ 2.8-3.6 κ(B)T greater than those for nontelomeric DNA. (Lin et. al., Nucleic Acids Res. 2014 Feb;42(4):2493-504.)
  • Reactive oxygen species (ROS)-induced DNA damage is repaired by the base excision repair (BER) pathway. A method was developed to specifically produce ROS-induced DNA damage by fusing KillerRed (KR), a light-stimulated ROS-inducer, to a tet-repressor (tetR-KR) or a transcription activator (TA-KR). Results showed that DNA glycosylases were efficiently recruited to DNA damage in heterochromatin, as well as in euchromatin. PARP1 was recruited to DNA damage within condensed chromatin more efficiently than in active chromatin. In contrast, recruitment of FEN1 was highly enriched at sites of DNA damage within active chromatin in a PCNA- and transcription activation-dependent manner. These results indicate that oxidative DNA damage is differentially processed within hetero or euchromatin. (Lan et. al., Nucleic Acids Res. 2014 Feb;42(4):2330-45.)

Members

Bakkenist, Christopher, PhD
Radiation Oncology
Luo, Jianhua, MD, PhD
Pathology
Bernstein, Kara, PhD
Microbiology and Molecular Genetics
O'Sullivan, Roderick, PhD
Pharmacology & Chemical Biology
Bruchez, Marcel, PhD
Chemistry
Opresko, Patricia, PhD
Environmental & Occupational Health
Chaillet, J. Richard, MD, PhD
Microbiology and Molecular Genetics
Prochownik, Edward, MD, PhD
Pediatrics (CHP)
Duncan, Andrew, PhD
Pathology
Sobol, Robert, PhD
Pharmacology & Chemical Biology
LaFramboise, William, PhD
Pathology
Van Houten, Bennett, PhD
Pharmacology & Chemical Biology
Lan, Li, MD, PhD
Microbiology and Molecular Genetics
Wan, Yong, PhD
Cell Biology