Tra1 is a 433 kDa component of the Saccharomyces cerevisiae SAGA and NuA4 transcriptional co-activator complexes. Tra1 interacts with transcriptional activators to recruit the complexes to specific promoters. As a PIKK (phosphoinositide three-kinase-related kinase) family member, Tra1 is characterized by a C-terminal phosphoinositide 3-kinase (PI3K) domain. Unlike other PIKK family members, Tra1 lacks kinase activity. The PI3K domain is still essential and mutations in this domain result in altered gene expression. To investigate the structure and function of Tra1’s PI3K domain, we are characterizing an allele we call tra1Q3 where three conserved arginine residues within the PI3K domain are mutated to glutamine. This allele results in slow growth under stress and decreased transcription activation. The protein mislocalizes to the cytoplasm and has decreased association with SAGA and NuA4. Pull downs of the mutant complexes also show altered interactions with SAGA-interacting proteins. Suppressors of tra1Q3 fall into the cleft of the kinase domain when mapped onto the known mTOR PI3K structure. Based on the reduced nuclear localization and failure to associate with SAGA and NuA4 demonstrated by this mutant, we believe the PI3K domain of Tra1 is important for the biosynthesis of Tra1 into SAGA and NuA4.