Establishment of DNA-DNA Interactions by the Cohesin Ring

Yasuto Murayama,Catarina P Samora,Yumiko Kurokawa,Hiroshi Iwasaki,Frank Uhlmann

doi:10.1016/j.cell.2017.12.021

Yasuto Murayama, Catarina P Samora + Show 3 more

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https://doi.org/10.1016/j.cell.2017.12.021

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Abstract

SummaryThe ring-shaped structural maintenance of chromosome (SMC) complexes are multi-subunit ATPases that topologically encircle DNA. SMC rings make vital contributions to numerous chromosomal functions, including mitotic chromosome condensation, sister chromatid cohesion, DNA repair, and transcriptional regulation. They are thought to do so by establishing interactions between more than one DNA. Here, we demonstrate DNA-DNA tethering by the purified fission yeast cohesin complex. DNA-bound cohesin efficiently and topologically captures a second DNA, but only if that is single-stranded DNA (ssDNA). Like initial double-stranded DNA (dsDNA) embrace, second ssDNA capture is ATP-dependent, and it strictly requires the cohesin loader complex. Second-ssDNA capture is relatively labile but is converted into stable dsDNA-dsDNA cohesion through DNA synthesis. Our study illustrates second-DNA capture by an SMC complex and provides a molecular model for the establishment of sister chromatid cohesion.

Highlights

Chromosome organization by structural maintenance of chromosome (SMC) complexes is vital for faithful chromosome segregation, DNA repair, and gene regulation
While cohesin and condensin are best known for their role in sister chromatid cohesion and chromosome condensation, respectively, the Smc5-Smc6 complex has been originally identified as a multi-subunit DNA repair complex with an essential but still incompletely understood role in chromosome segregation
Cohesin was incubated with these double-stranded DNA (dsDNA) beads in the presence of ATP and the cohesin loader, free circular DNA was added to the same reaction for further incubation. dsDNA beads were sedimented and washed in a high-salt buffer, and captured circular DNA was analyzed by agarose gel electrophoresis

Summary

Introduction

Chromosome organization by SMC complexes is vital for faithful chromosome segregation, DNA repair, and gene regulation. Deficiencies in SMC complexes and their regulators lead to a plethora of human malignancies, including developmental defects, infertility, and cancer (Liu and Krantz, 2008). SMC complexes are an evolutionarily conserved protein family that underpins genome organization in organisms, from bacteria to humans. Eukaryotes contain at least three essential family members: cohesin, condensin, and the Smc5-Smc complex. While cohesin and condensin are best known for their role in sister chromatid cohesion and chromosome condensation, respectively, the Smc5-Smc complex has been originally identified as a multi-subunit DNA repair complex with an essential but still incompletely understood role in chromosome segregation. A common feature of SMC complexes is that they bind to DNA by topological embrace (Hirano, 2016; Jeppsson et al, 2014; Nasmyth, 2011; Peters and Nishiyama, 2012; Uhlmann, 2016)

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