Disassembly of the bacteriophage Mu transposase for the initiation of Mu DNA replication

Abstract

Upon catalyzing strand transfer, the Mu transposase (MuA) remains tightly bound to the resulting transposition intermediate, the strand transfer complex (STC), and poses an impediment to host replication proteins. Additional host factors, which can be resolved into two fractions (Mu Replication Factor α and β; MRFα and MRFβ), are required to disassemble the MuA complex and initiate DNA synthesis. MRFα modifies the protein content of the STC, removing MuA from the DNA in the process. The MRFβ promotes initiation of Mu DNA synthesis on the STC altered by the MRFα. These host factors cannot promote initiation of Mu DNA synthesis if the STC is damaged by partial proteolysis. Moreover, the mutant protein MuA211 cannot be removed from the STC by MRFα, blocking initiation of DNA synthesis. These results indicate that MuA in the STC plays a critical function in beginning a sequence of events leading to the establishment of a Mu replication fork.