Research in Jim Paulson's lab
Dr. James Paulson (UW Oshkosh Chemistry Department) is a biochemist
whose research focuses on protein phosphorylation and dephosphorylation
at mitosis and its regulation, and induction of apoptosis (cell death)
in metaphase-arrested cells. The goal of these studies is to better
understand basic cell physiology and cell cycle dynamics.
Several projects suitable for REU students will be available. One will investigate the protein phosphatase (previously identified as PP1) that dephosphorylates histones H1 and H3 during exit from mitosis. We have developed a procedure to extract this enzyme from isolated mitotic chromosomes, and our goal is to partially purify it and identify the PP1 isotype and any regulatory or targeting subunit(s). This will be aided by peptide mass fingerprinting using MALDI-TOF, and sequence information obtained by applying post-source decay (PSD) to one or more tryptic fragments. Use of the Fluorescence Imager for phosphorimaging of 32P-labeled proteins will make possible a convenient assay during purification of the enzyme. A second project relates to our discovery that metaphase-arrested HeLa cells, unlike interphase cells, are very susceptible to induction of apoptosis by mild hyperthermia (39-41.5?C). Sensitivity depends on the length of time of the metaphase arrest, suggesting that it results from accumulation or depletion of specific cellular components . One possibility is that ceramides accumulate due to modulation of enzyme activity during mitosis. This will be tested by carrying out lipid fingerprinting on isolated mitochondria, comparing interphase and late-metaphase-arrested cells using HPLC and electrospray ionization mass spectrometry. Possible protein differences between early- and late-metaphase-arrested cells will be probed using differential staining (Cy-3 and Cy-5) and 2D-gel electrophoresis.
