Abstract 2121 Investigating the formation of protein complexes within the BREX bacterial defense system

The bacteriophage exclusion (BREX) system is a relatively uncharacterized, seven-gene bacterial defense system that carries out two main activities: phage restriction and host DNA methylation. However, the mechanism by which it performs these activities is unknown. Previous studies from our lab showed that host DNA methylation requires five of six conserved BREX genes, and that phage restriction requires all six genes. We hypothesize that BREX proteins carry out these activities by associating with each other into larger assemblages. In this study, we investigate the formation of complexes between various BREX factors using pull-down assays and purification of co-expressed proteins. We have identified several pairwise protein interactions as well as larger complexes containing multiple BREX components. Confirming these complexes is an essential step in determining their functional roles within BREX methylation and phage restriction mechanisms. This work was supported by an NIH R15 grant (award #1R15GM140375 to Brett K. Kaiser).