A new class of OLD family ATPases Cran1 functions in cell cycle progression in an archaeon

Overcoming lysogenization defect (OLD) proteins are diverse ATPases-nucleases functioning in antiphage defense in bacteria. However, the role of these proteins in archaea is currently unknown. Here, we describe a new class of archaeal OLD family ATPases and show that they do not appear to be involved in antiviral defense but play an essential role in cell cycle progression. The gene in Saccharolobus islandicus REY15A, named as Cran1 (Cell cycle related ATPase and nickase 1), cannot be deleted and exhibits cyclic expression patterns, with a peak expression during the transition from M-G1 to S cell cycle phase. Cran1 overexpression leads to significant growth retardation, cell size enlargement, and increased cellular DNA content. Cran1 displays potent nickase and ATPase activities in vitro, with the nickase activity being dependent on the presence of the ATPase domain. Notably, Cran1 copurifies with chromatin-associated proteins, such as Cren7 and a histone deacetylase homolog, suggesting its involvement in chromatin-related activities. Collectively our results suggest that Cran1 plays an important role in cell cycle progression, revealing a novel function of OLD family proteins.