Probing the mechanisms that couple genome segregation to chromosome organisation in Archaea
Lead Research Organisation:
JOHN INNES CENTRE
Abstract
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Technical Summary
Chromosome segregation is a fundamental process in all life forms. It requires the concerted action of dedicated proteins and coordination with cellular transactions, such as DNA organization, replication and cell division. The mechanisms that mediate this cell-cycle event in eukaryotes and bacteria are well established. In contrast, chromosome segregation is poorly defined in archaea, the third domain of life.
We have investigated a hybrid machine consisting of two interacting proteins, SegA and SegB, that play a key role in archaeal chromosome segregation. SegA is an orthologue of bacterial Walker ParA proteins. SegB is an archaea-specific DNA-binding factor that recognizes palindromic DNA motifs. Our ChIP-seq studies have revealed multiple SegB binding motifs scattered across the chromosome. Consistent with these results, microscopy has shown that SegB forms multiple foci on the chromosome, which then coalesce into large patches. Moreover, atomic force microscopy studies have shown that SegB bridges distant DNA sites, forming loop structures. These unpublished findings support the hypothesis that SegB might mediate chromosome organization prior to and in preparation for segregation. Moreover, recently we have solved the structures of SegA, SegB and respective DNA complexes, which provide snapshots into the mechanism of action of the proteins.
The overarching aim of the project is to establish the mechanisms through which the SegAB complex mediates genome segregation and how this process is coupled to chromosome organization. Cross-disciplinary approaches ranging from chromosome conformation capture and structured illumination microscopy to cross-linking mass spectrometry and cryo electron microscopy will provide transformative, multifaceted insights into the mechanism of action of the SegAB complex. The studies will open new perspectives on chromosome biology that will broaden mechanisms and principles established for the other two domains of life.
We have investigated a hybrid machine consisting of two interacting proteins, SegA and SegB, that play a key role in archaeal chromosome segregation. SegA is an orthologue of bacterial Walker ParA proteins. SegB is an archaea-specific DNA-binding factor that recognizes palindromic DNA motifs. Our ChIP-seq studies have revealed multiple SegB binding motifs scattered across the chromosome. Consistent with these results, microscopy has shown that SegB forms multiple foci on the chromosome, which then coalesce into large patches. Moreover, atomic force microscopy studies have shown that SegB bridges distant DNA sites, forming loop structures. These unpublished findings support the hypothesis that SegB might mediate chromosome organization prior to and in preparation for segregation. Moreover, recently we have solved the structures of SegA, SegB and respective DNA complexes, which provide snapshots into the mechanism of action of the proteins.
The overarching aim of the project is to establish the mechanisms through which the SegAB complex mediates genome segregation and how this process is coupled to chromosome organization. Cross-disciplinary approaches ranging from chromosome conformation capture and structured illumination microscopy to cross-linking mass spectrometry and cryo electron microscopy will provide transformative, multifaceted insights into the mechanism of action of the SegAB complex. The studies will open new perspectives on chromosome biology that will broaden mechanisms and principles established for the other two domains of life.
Organisations
People |
ORCID iD |
| Tung Le (Principal Investigator) |
 http://orcid.org/0000-0003-4764-8851
|
Publications
| Description | Chromosome segregation is a fundamental process in all life forms and requires coordination with genome organization, replication and cell division. The mechanism that mediates chromosome segregation in archaea remains enigmatic. Previously, we identified two proteins, SegA and SegB, which form a minimalist chromosome partition machine in Sulfolobales. Here we uncover patterns and mechanisms that SegAB employ to link chromosome organization to genome segregation. Deletion of the genes causes growth and chromosome partition defects. ChIP-seq investigations reveal that SegB binds to multiple sites scattered across the chromosome, but mainly localised close to the segAB locus in most of the examined archaeal genera. The sites are predominantly present in intragenic regions and enriched in one of the two compartments into which the chromosome folds. We show that SegB coalesces into multiple foci through the nucleoid, exhibiting a biased localisation towards the cell periphery, which hints at potential tethers to the cell membrane. Atomic force microscopy experiments disclose short-range DNA compaction and long-range looping of distant sites by SegB, pointing to a significant role for SegB in chromosome condensation that in turn enables genome segregation. Collectively, our data put forward SegAB as important players in bridging chromosome organization to genome segregation in archaea. |
| Exploitation Route | Still early to say as the award is still active, but we predict that fundamental insights from work in this award on SegAB will motivate the community to look at the problem of chromosome segregation and its coordination of cell division/cell cycle in this archaea Sulfolobus. And as archaea (rather than bacteria) is closer evolutionarily to eukaryotes, future work will potentially shed light on how fundamental processes in eukaryotes had evolved but using a simpler system for investigation. |
| Sectors | Education Environment Manufacturing including Industrial Biotechology |