ClpX protein of Escherichia coli activates bacteriophage Mu transposase in the strand transfer complex for initiation of Mu DNA synthesis.

Abstract

During transposition bacteriophage Mu transposase (MuA) catalyzes the transfer of a DNA strand at each Mu end to target DNA and then remains tightly bound to the Mu ends. Initiation of Mu DNA replication on the resulting strand transfer complex (STC1) requires specific host replication proteins and host factors from two partially purified enzyme fractions designated Mu replication factors alpha and beta (MRFalpha and beta). Escherichia coli ClpX protein, a molecular chaperone, is a component required for MRFalpha activity, which removes MuA from DNA for the establishment of a Mu replication fork. ClpX protein alters the conformation of DNA‐bound MuA and converts STC1 to a less stable form (STC2). One or more additional components of MRFalpha (MRFalpha2) displace MuA from STC2 to form a nucleoprotein complex (STC3), that requires the specific replication proteins and MRFbeta for Mu DNA synthesis. MuA present in STC2 is essential for its conversion to STC3. If MuA is removed from STC2, Mu DNA synthesis no longer requires MRFalpha2, MRFbeta and the specific replication proteins. These results indicate that ClpX protein activates MuA in STC1 so that it can recruit crucial host factors needed to initiate Mu DNA synthesis by specific replication enzymes.

von Hippel–Lindau binding protein 1-mediated degradation of integrase affects HIV-1 gene expression at a postintegration step

“…This process is catalyzed by the bacteriophage-encoded MuA transposase that remains tightly bound to the strand-transfer product at the Mu DNA ends after the strand-transfer reaction, thereby inhibiting assembly of the bacterial DNA-replication machinery and lytic growth (45). The recombination-replication transition of the Mu life cycle requires destabilization of the MuA-DNA complex by the bacterial chaperone molecule ClpX, which unfolds and releases a subset of MuA subunits from the strand-transfer complex, thus allowing recruitment of the replication machinery (46)(47)(48)(49). Similarly to Mu transposition, IN disassembly from the proviral DNA ends by the prefoldin-VHL-proteasome machinery after HIV-1 integration could be required for viral transcription to proceed.…”

Interaction of HIV-1 Integrase with DNA Repair Protein hRad18

“…This complex reaction is orchestrated by its transposase, MuA, in concert with both host and viral factors. After recombination is completed, the nucleoprotein complex (transpososome) is remodeled by the bacterial chaperone molecule ClpX (35,36) that specifically recognizes MuA and mediates its unfolding and eventually its destabilization (37). The susceptibility of HIV-1 integrase to rapid degradation by the ubiquitin/proteasome pathway N-end rule (14) and a recent report indicating that in vitro an excess of integrase inhibits closure of the DNA single strand intervals (11) seems to suggest that indeed the integration complex (intasome) needs to be disassembled for integration to be completed.…”

Replication terminus for DNA polymerase I during initiation of pAMβ1 replication: role of the plasmid‐encoded resolution system

“…However, an alternative model can be considered. It is based on the recent observation that the transposase of bacteriophage Mu (MuA) plays a critical role in preparing the product of the strand-transfer reaction (a MuA-DNA complex carrying branched structures) for assembly of a chromosomal-type replication fork (Kruklitis and Nakai, 1994;Nakai and Kruklitis, 1995;Kruklitis et al, 1996). In this model, the bound resolvase would act as a roadblock for Pol I progression and as a signal which causes a cascade of protein-protein interactions leading to Res␤ release and replisome assembly.…”