Functional assignment of multiple ESCRT‐III homologs in cell division and budding in Sulfolobus islandicus

Abstract

The archaea Sulfolobus utilizes the ESCRT-III-based machinery for cell division. This machinery comprises three proteins: CdvA, Eukaryotic-like ESCRT-III and Vps4. In addition to ESCRT-III, Sulfolobus cells also encode three other ESCRT-III homologs termed ESCRT-III-1, -2 and -3. Herein, we show that ESCRT-III-1 and -2 in S. islandicus REY15A are localized at midcell between segregating chromosomes, indicating that both are involved in cell division. Genetic analysis reveals that escrt-III-2 is indispensable for cell viability and cells with reduced overall level of ESCRT-III-1 exhibit growth retardation and cytokinesis defect with chain-like cell morphology. In contrast, escrt-III-3 is dispensable for cell division. We show that S. islandicus REY15A cells generate buds when infected with S. tengchongensis spindle shaped-virus 2 (STSV2) or when ESCRT-III-3 is over-expressed. Interestingly, Δescrt-III-3 cells infected with STSV2 do not produce buds. These results suggest that ESCRT-III-3 plays an important role in budding. In addition, cells over-expressing the C-terminal truncated mutants of ESCRT-III, ESCRT-III-1 and ESCRT-III-2 are maintained predominantly at the early, late, and membrane abscission stages of cell division respectively, suggesting a crucial role of the ESCRTs at different stages of membrane ingression. Intriguingly, intercellular bridge and midbody-like structures are observed in cells over-expressing MIM2-truncated mutant of ESCRT-III-2.

Live cell imaging of the hyperthermophilic archaeon Sulfolobus acidocaldarius identifies complementary roles for two ESCRTIII homologues in ensuring a robust and symmetric cell division

“…Also, whereas cdvB1 deletion cells could be generated in Sulfolobus islandicus [9], cdvB2 was found to be an essential gene in this organism. In addition, Liu and collaborators [30] observed distinct effects of overexpressing truncated versions of CdvB1 and CdvB2 in S. islandicus by imaging static cells at room temperature. In their study, the over-expression of the truncated versions of CdvB2 version generated cells with defects in the final stages of abscission [30] and protrusions similar to midbodies, whereas the overexpression of truncated CdvB1 generated a population of connected cells, similar to a chain.…”

Proteasome-mediated protein degradation resets the cell division cycle and triggers ESCRT-III-mediated cytokinesis in an archaeon

“…CdvB is part of the ESCRT-III-mediated cell division ring in archaea, and was previously suggested to be a core part of the cell division machinery (15)(16)(17)31). Given this, why would an increase in the level of this key division protein be associated with the inability to divide?…”

“…Proteomics then allowed us to identify a set of proteasomal targets involved in the final stages of the cell division cycle. We identify an archaeal ESCRT-III homologue, CdvB (Saci_1373), which is part of the CdvABC operon (Saci_1374, Saci_1373 and Saci_1372) and previously implicated in S. acidocaldarius cell division (15)(16)(17), as a key proteasomal target at the transition from the end of one cycle to the beginning of the next. Strikingly, our analysis suggests that CdvB inhibits cell division by preventing the constriction of another ESCRT-III ring, comprised of the CdvB paralogues CdvB1 (Saci_0451) and CdvB2 (Saci_1416).…”

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

“…[90] CdvA can bind to the membrane, so it is often modeled as the recruiter of CdvB to the membrane (Figure 7). [92] CdvCi nteracts with CdvB and is essential for abscission. [92] CdvCi nteracts with CdvB and is essential for abscission.…”

“…[91] CdvB is proposed to be important for early-stage division, andt he paralogues CdvB1 and CdvB2 are suggested to have roles in cellular abscission. [92] CdvCi nteracts with CdvB and is essential for abscission. [93] CdvB3 is thought to be important but not essential for cell divisiona nd CdvAl ocalization.…”