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Title | DNA-measuring Wadjet SMC ATPases restrict smaller circular plasmids by DNA cleavage. |
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Journal, issue, pages | Mol Cell, Vol. 82, Issue 24, Page 4727-44740.e6, Year 2022 |
Publish date | Dec 15, 2022 |
![]() | Hon Wing Liu / Florian Roisné-Hamelin / Bertrand Beckert / Yan Li / Alexander Myasnikov / Stephan Gruber / ![]() |
PubMed Abstract | Structural maintenance of chromosome (SMC) complexes fold DNA by loop extrusion to support chromosome segregation and genome maintenance. Wadjet systems (JetABCD/MksBEFG/EptABCD) are derivative SMC ...Structural maintenance of chromosome (SMC) complexes fold DNA by loop extrusion to support chromosome segregation and genome maintenance. Wadjet systems (JetABCD/MksBEFG/EptABCD) are derivative SMC complexes with roles in bacterial immunity against selfish DNA. Here, we show that JetABCD restricts circular plasmids with an upper size limit of about 100 kb, whereas a linear plasmid evades restriction. Purified JetABCD complexes cleave circular DNA molecules, regardless of the DNA helical topology; cleavage is DNA sequence nonspecific and depends on the SMC ATPase. A cryo-EM structure reveals a distinct JetABC dimer-of-dimers geometry, with the two SMC dimers facing in opposite direction-rather than the same as observed with MukBEF. We hypothesize that JetABCD is a DNA-shape-specific endonuclease and propose the "total extrusion model" for DNA cleavage exclusively when extrusion of an entire plasmid has been completed by a JetABCD complex. Total extrusion cannot be achieved on the larger chromosome, explaining how self-DNA may evade processing. |
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Methods | EM (single particle) |
Resolution | 3.0 - 3.52 Å |
Structure data | EMDB-15609, PDB-8as8: EMDB-16020, PDB-8bfn: |
Chemicals | ![]() ChemComp-ADP: |
Source |
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![]() | DNA BINDING PROTEIN / SMC complexes / bacterial immunity / defense system / DNA loop extrusion / Wadjet / JetABCD / DNA cleavage / plasmid restriction / mksBEFG / mobile genetic elements / horizontal gene transfer / eptABCD / mukBEF |