Fig. 7: Proposed model for the roles of BSL1 and CDKB1 in the control of mitosis in Chlamydomonas compared with animals.
From: Mitotic entry is controlled by the plant-specific phosphatase BSL1 and cyclin-dependent kinase B
In fungi and metazoans, mitosis is triggered by the activation of Cdk1, which is inactivated during replication stress by phosphorylation at Thr14/Tyr15 and subsequently activated by Cdc25-mediated dephosphorylation. Similarly, in Chlamydomonas, CDKB1 is essential for mitosis and is inactivated by phosphorylation at Thr14/Tyr15. However, the dephosphorylation of CDKB1 Thr14/Tyr15 is mediated by BSL1. In addition, BSL1 promotes CDKB1 accumulation independent of Thr14/Tyr15 dephosphorylation, possibly by inhibiting an unknown protein (X) that mediates CDKB degradation. +p/−p, phosphorylation/dephosphorylation. Triangular arrowheads indicate positive regulation, diamond-shaped arrowheads indicate inhibitory regulation and dashed lines indicate hypothetical mechanisms.
