UC San Diego

Malignant tumors are distinguished from normal cells by a number of hallmarks, including metabolic reprogramming and genome instability. Metabolic reprogramming in cancer cells was first observed by Otto Warburg in the early 20th century. Recently metabolic enzymes have been shown to be drivers of cancer. Isocitrate dehydrogenase 1 (IDH1) is a metabolic enzyme that has altered activity in cancer and drives tumorigenesis. Mutations in IDH1 are frequently observed in low grade gliomas and secondary glioblastomas. However, wild-type IDH1 is also overexpressed in primary glioblastomas and has been linked to the growth of these tumor types. The products of the IDH1 reaction are essential for many metabolic processes. Changes in the cellular environment, such as pH fluctuations, substrate concentration levels, and oxygen levels can reroute metabolism by modifying the activity of metabolic enzymes like IDH1. Amino acid residues that sense changes in pH will typically have a shifted pKa towards physiological pH levels. The change in pKa stores the potential energy required to drive a structural/functional modification that alters catalytic activity. A goal of this dissertation was to identify any pH-dependent activity in IDH1 and provide a mechanism for how it sensed changes in pH to regulate its catalytic activity. Accurate genome replication is essential to ensure the survival of offspring. Considering the size of the human genome and its constant exposure to environmental and endogenous damage, this is not an easy task, and is further complicated by a damage associated with cancer. A number of DNA polymerases have evolved to handle the bulk to DNA synthesis, repair, and overall genome maintenance. DNA Polymerase  is responsible for the highly accurate and processive DNA replication on the leading strand. The high-fidelity of DNA Polymerase  is maintained through a balance between its incorporation and proofreading activities. Mutations altering either of these abilities are frequently observed in endometrial cancer. The second goal of this thesis was to investigate mechanisms of (in)fidelity of polymerase domain mutants in DNA Polymerase .