A TFIIB paralog drives cyclic transcription to orchestrate the archaeal cell cycle

Cyclic transcription is a hallmark of the cell cycle. While transcriptional waves in eukaryotes are driven by oscillations in cyclin-dependent kinase (CDK) activity, many archaea have an ordered cell cycle despite lacking CDKs. Here in exploring how cyclic transcription is achieved in Sulfolobus acidocaldarius, we show that TFB2, a paralog of eukaryotic TFIIB, is cyclically expressed, associated with the promoters of division genes (including tfb2 itself), contains a cyclin-box and is degraded as cells exit division. Furthermore, a dominant-negative TFB2 mutant interferes with division gene expression and cytokinesis. These data identify TFB2 as a central player in the circuitry orchestrating the orderly cell cycle in Sulfolobus and, despite the absence of CDKs, reveal parallels between the regulatory logic of archaeal cell division and eukaryotic mitosis.