SpoIIIE strips proteins off the DNA during chromosome translocation

Abstract

The FtsK/SpoIIIE family of DNA transporters are responsible for translocating missegregated chromosomes after the completion of cell division. An extreme example of this post-cytokinetic DNA segregation occurs during spore formation in the bacterium Bacillus subtilis, where SpoIIIE pumps three-quarters of the chromosome (>3 megabases) into one of the two daughter cells. Here, we investigate the fate of the proteins associated with the translocated DNA. Taking advantage of several unique features of Bacillus sporulation, we demonstrate that RNA polymerase, transcription factors, and chromosome remodeling proteins are stripped off the DNA during translocation of the chromosome into the forespore compartment. Furthermore, we show that in vitro the soluble ATPase domain of SpoIIIE can displace RNA polymerase bound to DNA, suggesting that SpoIIIE alone is capable of this wire-stripping activity. Our data suggest that the bulk of the forespore chromosome is translocated naked into the forespore compartment. We propose that the translocation-stripping activity of SpoIIIE plays a key role in reprogramming developmental gene expression in the forespore.