The Skaggs Institute
for Chemical Biology

Scientific Report 2007

Training in Molecular and Experimental Medicine

E. Beutler

Exploring the experimental interface between the basic sciences of chemistry, biology, and clinical medicine requires specific technical training in a context that also provides a perspective encompassing both sides of the interface, if the exploration is to be more than just examining compounds for their activity in disease models. The Skaggs Institute for Chemical Biology has attempted to develop such explorers by supporting young scientists in the Department of Molecular and Experimental Medicine at Scripps Research.

Christian Nievera, under the tutelage of Xiaohua Wu, assistant professor in the Division of Molecular Oncology, is studying molecular mechanisms involved in cell-cycle arrest in response to DNA damage. Dr. Nievera is determining the role of the Mre11/Rad50/Nbs1 (MRN) complex and its interaction with replication protein A in modulating the S-phase checkpoint after DNA damage. He is examining whether the MRN complex directly inhibits DNA replication as well as being involved in transducing DNA damage signals. Because much of the natural resistance to malignant transformation due to mutational events appears to be related to the cells' capacity to preserve the integrity of DNA, an understanding of the mechanisms involved in these responses is critical.

Alan Yueh-Luen Lee, also working in Dr. Wu's group, has focused on the role of MRN in preventing re-replication of DNA after Cdt1 overexpression. Loss of the complex increases re-replication in susceptible cell lines but also leads to re-replication in cells normally resistant to the process. MRN apparently works by facilitating activation of the ataxia telangiectasia–mutated and Rad3-related (ATR) pathway to phosphorylate Chk1. The Nbs1 component of the MRN complex is also a substrate of ATR, and its phosphorylation at S343 by ATR occurs early after Cdt1 is overexpressed. The failure to phosphorylate leads to more aggressive re-replication. These studies draw attention to the critical role of the intact MRN complex in the process.

Jaroslav Truksa, a trainee in my laboratory in the Division of Hematology and Genetics, has been studying transcriptional regulation of hepcidin, a critical regulator of iron metabolism. Hepcidin appears to be particularly important in the anemia of chronic inflammation, one of the most common forms of anemia, and understanding of the function of hepcidin is also likely to provide insight into iron storage diseases. Dr. Truksa has used innovative methods, a luciferase reporter and in vivo bioluminescence, to study transcriptional regulation in intact animals. With this technology, he has defined an upstream region of the hepcidin promoter that is important in the response to ingested iron. Using tissue culture methods, he has defined a second, distinct region in the same promoter that responds to cytokine stimulation.

Zhengyi Ye is receiving his postdoctoral training from Professor Joel Buxbaum, head of the Division of Rheumatology Research. In studies on the physiologic role of the serum and cerebrospinal fluid protein transthyretin, Dr. Ye noted that a number of published reports suggested that cerebral transcription of the gene encoding the protein was increased in several neurodegenerative disorders, most prominently Alzheimer's disease. Using surface plasmon resonance, he showed that both murine and human transthyretin bound aggregates of the Alzheimer-associated amyloid β_1–40 and amyloid β_1–42 peptides but did not bind the peptide monomers. These data provided a mechanistic explanation of in vivo experiments in the Buxbaum laboratory, showing that overexpression of human transthyretin in a murine model of Alzheimer's disease suppressed the neuropathologic, behavioral, and biochemical phenotype; the same model had an accelerated course in mice in which the endogenous transthyretin had been silenced by targeted disruption.

Each of the trainees has fulfilled the goals of the Skaggs program by applying basic science knowledge and techniques to disease-related biologic systems. They have made or are making contributions to the understanding of the clinical disorders.