Biomedical Sciences ETDs

Publication Date



Exposure to ultraviolet radiation (UVR) promotes the formation of UVR-induced, DNA helix distorting photolesions such as (6-4) pyrimidine-pyrimidone photoproducts (6-4 PPs) and cyclobutane pyrimidine dimers (CPDs). Effective repair of such lesions by the nucleotide excision repair (NER) pathway is required to prevent DNA mutations and chromosome aberrations. Poly(ADP-ribose)polymerase-1 (PARP-1) is a zinc-finger protein with well documented involvement in base excision repair (BER). PARP-1 is activated in response to DNA damage and catalyzes the formation of poly(ADP-ribose) subunits (PAR) that assist in the assembly of DNA repair complexes at sites of damage. In this dissertation, I present evidence for PARP-1 contributions to NER, extending the knowledge of PARP-1 function in DNA repair beyond the established role in BER. Silencing the PARP-1 protein or inhibiting PARP activity leads to retention of UVR-induced photolesions in vitro and in vivo. PARP activation following UVR exposure promotes association between PARP-1 and XPC, a central protein in lesion recognition in the global genomic arm of NER. Additionally, PARP activation following UVR promotes association with XPA, an essential protein in NER that is involved in DNA damage verification and stability of the preincision complex. Both proteins are predicted to contain the well defined 25 amino acid PAR binding sequence. Administration of PARP inhibitors confirms that PAR facilitates PARP-1 association with XPA and XPC in whole cell extracts as well as in isolated chromatin complexes; and illustrates the importance of the PAR binding sequence in PARP-1s interaction with NER proteins. Furthermore, inhibition of PARP activity decreases UVR-stimulated XPA and XPC chromatin association. These data not only illustrate that these relationships occur in the meaningful context for NER, but they also demonstrate a novel role for PAR as a potential modulator of NER proteins. Overall, these results provide a mechanistic link for PARP activity in the repair of UVR-induced photoproducts which could potentially be useful in the development of new combinations of cancer chemotherapy drugs.


"NER, PARP, DNA repair, ultraviolet radiation, XPA, XPC"

Document Type




Degree Name

Biomedical Sciences

Level of Degree


Department Name

Biomedical Sciences Graduate Program

First Committee Member (Chair)

Liu, Ke Jian

Second Committee Member

Allan, Andrea

Third Committee Member

Timmins, Graham

Fourth Committee Member

Liu, Wenlan