Archaeal cell cycle regulation

Although the archaeal domain basically possesses a prokaryotic type of cell strueture, the archaebacteria share many molecular features with eukaryotes, in particular the mechanisms for chromosome replication and gene expression. Several homologs of cell. -cycle control (Cdc) proteins, which in eukaryotes have been implicated in the regulation of DNA replication, have been identified in Archaea, implying a similar mechanism of cell-cycle regulation. In addition, the archaeal cell-cycle often includes a sho rt pre--replication period but an extensive post-replicative stage, thus being different from eubacteria while sharing similarities with the eukaryotic cell-cycle pattern. We intend to use Archaeoglobus fulgidus, a hyperthermophilic archaeon growing optim ally at 83oC, for further investigations of the archaeal cell-cycle pattern and its regulation, mapping and analysis of the origin of DNA replication, as well as elucidation of the possible role(s) of the A. fulgidus Cdc homologs in replication initiation. The cell-cycle pattern and replication origin will be analysed and mapped using flow cytometry and marker frequency analyses, respectively. The function of the Cdc proteins will be elucidated using various DNA-binding assays, structural analy ses, and development of an in vitro system for initiation of archaeal DNA replication. The results also have implications for the understanding of cell-cyele regulation in eukaryotes. n