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In C. elegans, HAM-1 is an asymmetrically localized protein that regulates several asymmetric neuroblast divisions. Although the protein contains a putative DNA binding domain, nuclear localization of HAM-1 has never been observed through immunostaining of embryos with anti-HAM-1 antibodies. However, a GFP::HAM-1 fusion protein has been detected in the nucleus of transgenic animals under direct fluorescence microscopy. Through a biochemical subcellular fractionation of embryonic extracts, I determined that endogenous HAM-1 is primarily a nuclear protein. I have also examined HAM-1 localization in different ham-1 mutant embryos. This analysis has revealed several key residues in the N-terminus and a region in the C-terminus that are required for proper cortical localization of HAM-1. Finally, I have shown that Tyrosine residue 369 is crucial for HAM-1 function. Thus, my work has lent insight into HAM-1 sequences that contribute to function and localization of the protein.
