Cell-specific SpoIIIE assembly and DNA translocation polarity are dictated by chromosome orientation.
SpoIIIE and FtsK are related proteins that translocate chromosomes across septa. Previous results suggested that SpoIIIE exports DNA and that translocation polarity is governed by the cell-specific regulation of its assembly, but that FtsK is a reversible motor for which translocation polarity is governed by its DNA substrate. Seeking to reconcile these conclusions, we used cell-specific GFP tagging to demonstrate that SpoIIIE assembles a complex only in the mother cell, from which DNA is exported, but that DNA translocation-defective SpoIIIE proteins assemble in both cells. Altering chromosome architecture by soj-spo0J and racA soj-spo0J mutations allowed wild-type SpoIIIE to assemble in the forespore and export the forespore chromosome. Combining LacI-CFP tagging of oriC with time-lapse microscopy, we demonstrate that the chromosome is exported from the forespore when oriC fails to be trapped in the forespore. Thus, the position of oriC after septation determines which cell will receive the chromosome and which will assemble SpoIIIE.
Becker
Eric C
EC
Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive La Jolla, CA 92093-0377, USA.
Pogliano
Kit
K
D001412:Bacillus subtilis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002876:Chromosomes, Bacterial / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D056968:Lac Repressors; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D051738:Origin Recognition Complex / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics; D013171:Spores, Bacterial / Q000737:chemistry / Q000378:metabolism*
D001426:Bacterial Proteins; C485182:Cyan Fluorescent Protein; D004269:DNA, Bacterial; D056968:Lac Repressors; D050505:Mutant Proteins; C114650:OriC chromosomal replication origin; D051738:Origin Recognition Complex; D012097:Repressor Proteins; C030069:spore-specific proteins, Bacillus; D049452:Green Fluorescent Proteins