Thomas Tan

Thomas Tan

PhD student, Biochemistry Department

Background:

Research Assistant, The Kuzell Institute for Arthritis and Infectious Diseases, California Pacific Medical Center, San Francisco, 1996-1997
BA in Molecular and Cell Biology with an emphasis in Biochemistry, University of California at Berkeley, 1996
Undergraduate research in the lab of Dr. Daniel E. Koshland, Jr. University of California at Berkeley, 1995-1996

Publications:

Kolodziej AF, Tan T, Koshland DE Jr. Producing positive, negative, and no cooperativity by mutations at a single residue located at the subunit interface in the aspartate receptor of Salmonella typhimurium. Biochemistry. 1996 Nov 26;35(47):14782-92.
Tan T, Chu G. p53 Binds and activates the xeroderma pigmentosum DDB2 gene
in humans but not mice. Mol Cell Biol. 2002 May;22(10):3247-54.

Research:
Ultraviolet (UV) radiation exposure can lead to DNA lesions such as cyclobutane pyrimidine dimers (CPDs) or 6-4 photoproducts. In addition, chemicals such as benzo[a]pyrene (found in cigarettes) and the chemotherapeutic drug, cisplatin, can lead to DNA damage. Such forms of DNA damage are removed by nucleotide excision repair (NER). The UV-damaged DNA binding protein (UV-DDB), which is composed of the DDB1 and DDB2 proteins, can bind to damaged DNA. DDB2 is important for global genomic repair of CPDs. Interestingly, rodent fibroblast cells are deficient in GGR of CPDs, in contrast to human cells. The human DDB2 gene is up regulated by p53. The p53 protein is involved in DNA repair, apoptosis, and cell cycle arrest. UV can activate p53, which in turn, can transcriptionally activate the DDB2 gene. We found a p53-responsive binding site in the human DDB2 gene. In contrast, the cognate site in the mouse DDB2 gene was unresponsive to p53. We also showed that the entire mouse DDB2 gene is unresponsive to p53 and UV. It appears that rodents lack p53 regulation of their DDB2 gene and subsequently lack GGR of CPDs in their skin. This might be explained by the fact that rodents are nocturnal animals and have fur to shield them from UV radiation. Interestingly, mice express DDB2 in the liver, where detoxification of chemicals takes place.We are currently investigating the role of DDB2 in the repair of chemical damage.

Hobbies: Racquetball, basketball, soccer, softball, running, weight training, indoor rock climbing, volleyball, bowling, dancing, listening to music, helping Joe gather free food.