MukBEF, a Chromosomal Organizer

Abstract

Global folding of bacterial chromosome requires the activity of condensins. These highly conserved proteins are involved in various aspects of higher-order chromatin dynamics in a diverse range of organisms. Two distinct superfamilies of condensins have been identified in bacteria. The SMC-ScpAB proteins bear significant homology to eukaryotic condensins and cohesins and are found in most of the presently sequenced bacteria. This review focuses on the MukBEF/MksBEF superfamily, which is broadly distributed across diverse bacteria and is characterized by low sequence conservation. The prototypical member of this superfamily, the Escherichia coli condensin MukBEF, continues to provide critical insights into the mechanism of the proteins. MukBEF acts as a complex molecular machine that assists in chromosome segregation and global organization. The review focuses on the mechanistic analysis of DNA organization by MukBEF with emphasis on its involvement in the formation of chromatin scaffold and plausible other roles in chromosome segregation.

Chromosome disentanglement driven via optimal compaction of loop-extruded brush structures

“…Bacteria, unlike eukaryotes, do not have nucleosomes; instead, bacterial DNA inside cells is coated with a variety of nucleoid-associated proteins (NAPs), e.g., HU, H-NS and IHF [49]. Like eukaryotes, bacteria possess SMC proteins (in E. coli, MukBEF [50]) and bacterial versions of eukaryote TopoII. We treat bacterial chromosomes as self-avoiding polymers, with cylindrical monomer units of length a ≈ 50 nm (comparable to the persistence length of naked DNA [51]) and width b ≈ 5 nm, corresponding to the thickness of protein-bound DNA segments (NAPs can reduce the persistence length but this is not crucial here).…”

Functional Modules of Minimal Cell Division for Synthetic Biology

“…Therefore, an important challenge facing bacterial cells is to compact their genome without compromising DNA processing. Physical and biochemical factors, such as interactions with ongoing replication and transcription processes [10] as well as structuring by the condensin structural maintenance of chromosomes (SMC) [11] or its functional homolog MukBEF [12] organize and condense the chromosome, as has been recently shown using chromosome conformation capture techniques. [6] Due to polymer dynamics a chromosome should spontaneously shape into a soft globule, accounting for an ≈100-fold compaction.…”

“…[7] Moreover, crowding conditions in a cell [8,9] and supercoiling by torsional stress result in DNA compaction and folding. Physical and biochemical factors, such as interactions with ongoing replication and transcription processes [10] as well as structuring by the condensin structural maintenance of chromosomes (SMC) [11] or its functional homolog MukBEF [12] organize and condense the chromosome, as has been recently shown using chromosome conformation capture techniques. [13][14][15][16] Chromosomal organization and compaction results in a discrete but dynamic coiled structure, whose shape depends on the geometry of the cell.…”

Lessons from a Minimal Genome: What Are the Essential Organizing Principles of a Cell Built from Scratch?

“…[8] How then is its chromosome segregated? E. coli also lacks aP ar system,b ut encodes for an SMC complex called MukBEF (reviewed in Rybenkov et al [47] ). It has been proposed that the extrusion of DNA from replication forks might help to push the sister chromosome copiest oward opposite sideso ft he cell ( Figure 5).…”