SUMOylation of Barrier-to-Autointegration Factor
de la Plante, Alexandra
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Barrier-to-autointegration factor (BAF) is an abundant and highly-conserved protein in eukaryotic cells, found in both the nucleus and cytoplasm. BAF interacts with endogenous and foreign DNA, and several classes of proteins, including histones, lamins, and LEM-domain proteins. BAF has been implicated in multiple cellular processes with roles in immune defense, nuclear envelope reassembly, cell cycle progression, and epigenetic regulation. BAF’s activities and patterns of distribution are in part regulated by phosphorylation. However, there are gaps in the current understanding of BAF function and regulation, in terms of its protein-binding activity in the nucleus and its patterns of cellular distribution. The possibility that BAF is regulated by additional post-translational modifications has yet to be investigated. My thesis project aimed to determine whether BAF undergoes post-translational modification in the form of SUMOylation, and to determine the effect(s) of this modification on BAF’s localization and protein-binding activity. My data suggest BAF is modified by SUMO2, and that the modified amino acids are K53 and K54. My data also suggest that SUMOylation does not affect BAF’s nuclear-cytoplasmic localization, nor does it affect BAF’s interaction with inner nuclear membrane proteins, emerin and lamin A. Further studies are required to determine the biological role(s) of BAF’s SUMOylation. However, results from the analysis of residues L52 and D55 in BAF’s apparent SUMO binding motif suggest a role of this site in SUMOylation-independent nuclearcytoplasmic localization of BAF and co-localization of BAF with emerin and lamin A.