O-GlcNAc Transferase (OGT) is an enzyme found in humans that adds a single sugar, O-linked beta-N-acetylglucosamine (O-GlcNAc), to over 1000 different nuclear and cytoplasmic proteins. Because of this, it regulates many important cellular processes critical for cell development and survival, but how OGT selects its large range of targets is unclear. OGT has two domains: the catalytic domain, which is responsible for sugar transfer, and the tetratricopeptide repeat (TPR) domain, which consists of 13.5 repeats. The TPR domain mainly participates in protein-protein interactions (PPIs) and is believed to influence how OGT selects its protein targets. To gain a better understanding of how protein-protein interactions control OGT’s function, it is essential to evaluate the different regions of the TPR domain. Our lab has shown that TPR 1 interacts with numerous proteins, even though it is the repeat furthest away from the catalytic domain. OGT exists in two forms, a monomer and a dimer; however, it is currently unknown which form is favored in different PPIs. To determine which form is required for interactions at TPR 1, we utilized site-directed mutagenesis to add a mutation into OGT that prevents it from dimerizing. Then, the mutated OGT was used to determine the changes in OGT’s interactions at TPR 1 with individual proteins and cellular extracts. These studies provide key insights into how OGT interacts with different proteins and will enable future studies on how OGT can selectively modify its targets.