Biology subjects

Traparic, J.

Publications and source records attributed to Traparic, J..

3 recordsLinked to original sources

bioRxiv2025

The mechanism of cell cycle dependent proteasome-mediated CdvB degradation in Sulfolobus acidocaldarius

Protein degradation helps order events in the cell division cycle in eukaryotes, bacteria and archaea. This process is best understood in eukaryotes, where chromosome segregation and mitotic exit are triggered by APC/C and ubiquitin-regulated proteasome-dependent degradation of Securin and Cyclin B, respectively. Recent findings show that the archaeal proteasome also targets cellular substrates, including CdvB, for degradation in a cell cycle-dependent manner in Sulfolobus acidocaldarius - one of the closest experimentally tractable archaeal relatives of eukaryotes. Here, using CdvB as a model target protein to explore the mechanism of cyclic protein degradation, we identify the C-terminal broken winged helix of CdvB, which was previously shown to bind CdvA, as a domain that is sufficient to render a fusion protein unstable as cells transit from division phase to G1 phase. In parallel, we show that the rate of CdvB degradation accelerates during division, in part due to a cell cycle-dependent increase in the expression of the proteasome-activating nucleotidase (PAN), under the control of a cyclically expressed novel transcription factor, "CCTF1" (saci_0800), that can repress PAN expression. Taken together, our findings reveal the mechanisms by which archaea, despite lacking CDK/cyclin or APC/C proteins, regulate proteasome-mediated degradation to order events during cell division.

cell biology↗

bioRxiv2025

A temperature sensitive mutant screen reveals translational stress-induced cell cycle regulation in a thermophilic archaeon

The homology of the archaeal and eukaryotic ribosome provides one of the key pieces of evidence that underpins the idea that eukaryotes acquired their core information processing machinery from archaea. Since this discovery, reverse genetics has been used to study the functions of many archaeal proteins with eukaryotic homologues. Yet, our general understanding of archaeal growth and division remains unclear, in part because of difficulties of carrying out unbiased genetic screens in archaea. Here, by overcoming several technical hurdles we have used a screen of temperature sensitive mutants in Sulfolobus acidocaldarius to identify core regulators of cell growth and division. First, flow cytometry was used to define DNA content, identifying a set of mutants defective in cell cycle progression at elevated growth temperatures. Using genome sequencing and plasmid rescue, we then identified a point mutation in the large ribosomal subunit that inhibits translation and prevents entry into division following a shift to the restrictive temperature. This study reveals a link between translation and cell cycle control, and opens up the future possibility of using forward genetic screens in archaea to further our understanding of the similarities and differences in the cell biology of archaea, bacteria and eukaryotes. Significance statementO_LICurrent knowledge of archaeal cell biology is limited by the lack of forward genetics. C_LIO_LIWhole genome sequencing and plasmid rescue identifies causative mutation in a temperature sensitive mutant strain. C_LIO_LIA mutation in a ribosomal subunit blocks translation to prevent entry into division. C_LI

cell biology↗

bioRxiv2022

The patterned assembly and stepwise Vps4-mediated disassembly of composite ESCRT-III polymers drives archaeal cell division

ESCRT-III family proteins form composite polymers that deform and cut membrane tubes in the context of a wide range of cell biological processes across the tree of life. In reconstituted systems sequential changes in the composition of ESCRT-III polymers induced by the AAA ATPase Vps4 have been shown to remodel membranes. However, it is not known how composite ESCRT-III polymers are organised and remodelled in space and time in cells. Here, taking advantage of the relative simplicity of the ESCRT-III-dependent division system in Sulfolobus acidocaldarius, one of the closest experimentally tractable prokaryotic relative of eukaryotes, we use super-resolution microscopy and computational modelling to show how CdvB/CdvB1/CdvB2 proteins form a precisely patterned composite ESCRT-III division ring which undergoes stepwise Vps4-dependent disassembly and contracts to cut cells into two. These observations lead us to suggest sequential changes in a patterned composite polymer as a general mechanism of ESCRT-III-dependent membrane remodelling.

cell biology↗