Celia
Tan
Sponsor: Francis Mcnally, Ph.D. Ag Molecular & Cellular Bio Positioning of the meiotic spindle at the cell cortex is a conserved process required for correct chromosome segregation during embryogenesis. Our laboratory previously discovered that kinesin-dependent inward packing of mitochondria is sufficient for cortical spindle positioning in Caenorhabditis elegans oocytes through volume-exclusion. These experiments were conducted using optogenetic tools, SSPB and iLID, which, when illuminated with blue light, artificially connect a protein of interest to constitutively active kinesin without a wild-type cargo-binding domain. Our previous work showed the fusion between LMP-1, lysosomal membrane protein-1, and GFP::SSPB, SSPB attached to green fluorescent protein, labels the plasma membrane in addition to lysosomes. We hypothesized this was due to GFP::SSPB relocating LMP-1 to the plasma membrane. As a control, we generated a C. elegans strain containing mCherry::pH, a red fluorescent plasma membrane marker, and GFP::SSPB alone. Live imaging of unfertilized oocytes in adult C. elegans hermaphrodites under a spinning disk confocal microscope revealed that GFP::SSPB localized to the plasma membrane and the nuclear envelope. These findings validate our hypothesis that SSPB targets to the plasma membrane on its own and will inform future studies that use optogenetic tools to research the role of spindle positioning in chromosome segregation. Structure Function Analysis of BRCA2 Protein Domains
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Celia Tan
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The BRCA2 protein functions as a tumor suppressor, regulating genome stability by facilitating assembly of RAD51-ssDNA filaments central to homologous recombination for DNA repair and replication processes. Loss of the functional BRCA2 results in accumulation of mutations from defective DNA repair causing cancer. The protein can be divided into the N terminus, the middle domain, and C terminus. It is presently unclear whether the middle domain, composed of 8 BRC repeats, contains another DNA binding element and what the functional significance of the helical and tower domains located in the C terminus are. This project aims to define the DNA binding regions in BRCA2 and how they function within the context of the full-length protein. Towards this end, we have created three plasmid constructs-full length BRCA2 open reading frame, mutant BRCA2 genes with a deletion of the helical domain or tower domain. We have transfected the plasmids into human HeLa cells to express the desired proteins. We will then compare the purified mutant proteins against the wild type to investigate the function of the targeted domains. DNA binding is a fundamental property of BRCA2, and our analysis will define the DNA binding properties of the various elements involved. Expression and Purification of the RAD54 Motor and C-terminal Domains to Study Their Interaction with RAD54B Protein in Homologous Recombination Runtong Tan
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UC Davis / Microbiology & Molec Genetics / 2026
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Celia Tan