Li Lan, MD, PhD
Dr Lan's Lab is focusing on analyzing DNA damage response chromatin remodeling mechanisms at specific genome loci.
Eukaryotic cells produce chromatin remodeling factors (CRFs) to increase the accessibility of repair enzymes to DNA lesions in the context of chromatin.
ACF1 and CHD5 are CRFs that contain ATPase remodeling and chromatin binding domains, however, their role in DNA repair is largely unknown. Defects in both the repair of DNA damage and in CRFs are implicated in tumorigenesis, but their interplay is not understood. To understand the damage responses of repair and CRFs in cells, we have established novel systems to produce either a mixture or a specific type of DNA damage in situ: 1. a UVA Laser Micro-Irradiation System produces a mixture of SSB, DSB and base damage; 2. an XPA-UVDE cell line irradiated with local UVC specifically induces SSB; 3. the I-SCEI endonuclease specifically induces DSB in human cells. We have used these experimental systems to screen the CRFs that might be involved in damage response and repair, in order to understand how repair is affected by CRF function. We found a novel tumor suppressor gene, CHD5, which is recruited to sites of DNA damage and necessary for repair. We will identify the role chromatin remodeling and histone modifications in tumorigenesis using in situ approaches and in vitro studies. We will analyze the precise mechanisms of CRF function in repair using in vivo and in vitro methods.
Environmental and endogenous reactive oxygen species (ROS) induced DNA base damage and single strand breaks block DNA replication, thereby leading to genome instability and genetic alterations. Therefore, understanding the dynamics of DNA damage response (DDR) in living cells will have broad implications for our understanding of the root cause of cancer and diseases.
We developed a visualization of DNA damage response at the single molecule level in real time using a novel method for expressing KillerRed, a marker of defined chromatin sites of DNA damage in human cells.
KillerRed photosensitizers are chromophores that generate natural ROS that induce DNA damage upon light irradiation. We have established a tetracycline responsive element (TRE) integrated U2OS cell line at defined sites of chromatin and tagged KillerRed with the tetracycline repressor (tetR). Via the interaction of tetR and TRE, KillerRed will be expressed at defined sites of the genome. We will define the DDR and mechanisms of current chromatin remodeling factors using this novel system. We also have developed a system to visualize the DNA damage response at the site of telomere. The effects of ROS damage at the sites of telomere on telomere integrity, cell death is going to be analyzed. The function of early aging Werner syndrome gene, WRN protein, will be analyzed.
Dr. Lan conducts her research at the University of Pittsburgh Cancer Institute.
Xiukai Chen, Visiting Scholar
Rong Tan, Health Science Fellow
Jacqueline Welty, Graduate Student