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Structures of archaeal DNA segregation machinery reveal bacterial and eukaryotic linkages

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Science  04 Sep 2015:
Vol. 349, Issue 6252, pp. 1120-1124
DOI: 10.1126/science.aaa9046

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Plasmid partitioning superstructure system

Partitioning and sharing DNA between dividing cells is critical for all domains of life. Prokaryotes must share certain plasmids as well as their genomic DNA to survive. Schumacher et al. studied the partition system that segregates a conjugative plasmid in the prokaryote Sulfolobus. The system consists of three proteins. AspA spreads along the plasmid DNA to create a protein-DNA superhelix. The ParA motor protein is linked to the protein-DNA superhelix through the ParB protein, which has structural similarities to eukaryotic centromere segregating proteins.

Science, this issue p. 1120

Abstract

Although recent studies have provided a wealth of information about archaeal biology, nothing is known about the molecular basis of DNA segregation in these organisms. Here, we unveil the machinery and assembly mechanism of the archaeal Sulfolobus pNOB8 partition system. This system uses three proteins: ParA; an atypical ParB adaptor; and a centromere-binding component, AspA. AspA utilizes a spreading mechanism to create a DNA superhelix onto which ParB assembles. This supercomplex links to the ParA motor, which contains a bacteria-like Walker motif. The C domain of ParB harbors structural similarity to CenpA, which dictates eukaryotic segregation. Thus, this archaeal system combines bacteria-like and eukarya-like components, which suggests the possible conservation of DNA segregation principles across the three domains of life.

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