RAD6-18 interactions with translesion synthesis polymerases, Pol H and Rev1

Every day a war is fought in our cells against nature’s missiles of ultraviolet waves, reactive oxygen species, and other chemicals that ravage our cell’s genetic material, DNA. As cells duplicate (aka replicate) their DNA in preparation for cell division, such damage poses an even greater risk to the cell. Damaged DNA in the path of replicating DNA causes a road-block in this process. This in turn may result in derailment of replication and breaks in the DNA. To prevent this, cells turn to a nanomachine, the bypassossome, that specializes in duplicating damaged DNA. However, the bypassossome often cause mutations in the DNA which can lead to new diseases and cancer cells. In order to walk the fine line between derailing replication and generating new cancer cells, this nanomachine must be tightly regulated. In this thesis, I discuss regulation of damaged DNA replication through the kick-starter of the nanomachine, Rad6-18. I discovered that Rad6-18 triggers the assembly of the nanomachine by allowing a duplicator protein, polymerase η, to “piggy-back” with Rad6-18 to the bypassossome. In addition, I also discovered that Rad6-18 has a switch that either prevents or allows Rad6-18 to contact a second, more error-prone duplicator protein, Rev1. In this way, Rad6-18 can chose to only add the error prone Rev1 into the nanomachine when absolutely necessary and thus prevent mutations. Our studies lead us to the hypothesis that the bypassossome is tightly regulated by Rad6-18 controlling the assembly of each polymerase to the bypassossome.