Eukaryotic DNA replication: 1) identifiation and characterization of potential target protein(s) involved in the regulation of DNA replication. 2) analyses of the molecular mechanisms that regulate DNA replication in response to extracellular signals, particularly DNA damage.
Molecular mechanism of non-homologous end joining repair in humans; Recognition of cisplatin-induced DNA damage in the early stage of nucleotide excision repair.
The human genome is littered with sequences derived fromtransposable elements from the Hsmar1 transposon, but there is only one intact copy of the Hsmar1 transposase gene termed Metnase (also known as SETMAR) that exists within a chimeric SET-transposase fusion protein. Although Metnase retains most of the transposase activities, it has evolved as a double-strand break (DSB) repair protein in anthropoid primates. Metnase is localized on chromosome 3p26, a region of frequent abnormalities in various cancers and is highly expressed in most tissues and cell lines. Mutations in Metnase that cause early termination were found in many transformed cell lines, although clinical relevance of these mutations has not been established. Our long-term goal is to understand how a protein with transposase activity in humans promotes DSB repair and chromosome decatenation, and what role the SET domain may play. Given that Metnase requires both the SET and transposase domains for its function(s) in DSB repair, we hypothesize that the acquisition of new functions may have resulted from a chimeric fusion between transposase and the SET domains. Our ongoing study is to elucidate the mechanism of this human SET-transposase protein in DSB repair and chromosome decatenation.
My lab is also interested in cisplatin damage and its repair in humans. Cisplatin is a widely used anti-cancer chemotherapeutic drug that induces DNA damage by forming cisplatin-DNA adducts in cells. In vivo and in vitro studies strongly suggest that most of the cisplatin-DNA adducts are repaired through nucleotide excision repair (NER) pathway. Due to extensive efforts, we now know a great deal about the mechanism of NER. Recognition of DNA damage is a critical step in the early stage of repair. Xeroderma pigmentosum group A complementing protein (XPA), replication protein A (RPA), XPC-hHR23B, and XPE can independently bind to damaged DNA. However, it is still in debate how the damage recognition proteins function at the damaged DNA site. We use biochemical and molecular approaches to analyze the role(s) of damage recognition proteins in the early stage of DNA repair. We are particularly interested in structural distortion of cisplatin-damaged DNA, a step essential for dual incision, but poorly understood.
