Chromosome segregation in Archaea mediated by a hybrid DNA partition machine

Eukarya and, more recently, some bacteria have been shown to rely on a cytoskeleton-based apparatus to drive chromosome segregation. In contrast the factors and mechanisms underpinning this fundamental process are underexplored in archaea, the third domain of life. Here we establish that the archaeo...

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Veröffentlicht in:Proceedings of the National Academy of Sciences - PNAS 2012-03, Vol.109 (10), p.3754-3759
Hauptverfasser: Kalliomaa-Sanford, Anne K., Rodriguez-Castañeda, Fernando A., McLeod, Brett N., Latorre-Roselló, Victor, Smith, Jasmine H., Reimann, Julia, Albers, Sonja V., Barillà, Daniela
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Sprache:eng
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Zusammenfassung:Eukarya and, more recently, some bacteria have been shown to rely on a cytoskeleton-based apparatus to drive chromosome segregation. In contrast the factors and mechanisms underpinning this fundamental process are underexplored in archaea, the third domain of life. Here we establish that the archaeon Sulfolobus solfataricus harbors a hybrid segrosome consisting of two interacting proteins, SegA and SegB, that play a key role in genome segregation in this organism. Seg A is an ortholog of bacterial. Walker-type ParA proteins, whereas SegB is an archaea-specific factor lacking sequence identity to either eukaryotic or bacterial proteins, but sharing homology with a cluster of uncharacterized factors conserved in both crenarchaea and euryarchaea, the two major archaeal sub-phyla. We show that SegA is an ATPase that polymerizes in vitro and that SegB is a site-specific DNA-binding protein contacting palindromic sequences located upstream of the segAB cassette. SegB interacts with SegA in the presence of nucleotides and dramatically affects its polymerization dynamics. Our data demonstrate that SegB strongly stimulates SegA polymerization, possibly by promoting SegA nucleation and accelerating polymer growth. Increased expression levels of segAB resulted in severe growth and chromosome segregation defects, including formation of anucleate cells, compact nucleoids confined to one half of the cell compartment and fragmented nucleoids. The overall picture emerging from our findings indicates that the SegAB complex fulfills a crucial function in chromosome segregation and is the prototype of a DNA partition machine widespread across archaea.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1113384109