The behaviour of mitotic kinases CDKB1 and WEE1 after DNA damage in Chlamydomonas reinhardtii
Monika Hlavová1, Mária Čížková1, Dáša Umysová1, Milada Vítová1, James G. Umen2, Kateřina Bišová1, and Vilém Zachleder1
1) Laboratory of Cell Cycles of Algae, Institute of Microbiology, ASCR, 37981 Třeboň, Czech Republic, 2) Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
Genomes of all organisms are exposed to various stress factors. Therefore it is vital for the cell to continuously check the integrity of genetic material and repair it immediately when damaged. DNA damage response pathway is protein network responsible for sensing, reacting to and repairing of damaged DNA. Two related kinases are involved in this pathway: ATM, which is activated by double-strand breaks, and ATR primarily responsing to single-strand breaks or stalled replication forks. In animals activated ATM/ATR trigger pathway leading to cell cycle arrest by regulation of CDC25 and WEE1. Plants lack a functional homolog of CDC25 and DNA damage checkpoint is controlled by WEE1 kinase operating in ATM/ATR dependent manner. In the model organism, green alga Chlamydomonas reinhardtii there is one homolog of each CDKB1 and WEE1 kinases. The roles of both proteins in the regulation of C. reinhardtii cell cycle are unknown. We analyzed expression and activity of CDKB1 and WEE1 in the response to DNA damage. Both of the genes are transcriptionally induced upon DNA damage and post-transcriptionally regulated in caffeine dependent manner leading to a cell cycle arrest prior to S/M phase with inactive CDKB. We conclude that algal CDKB1 is mitotic kinase in contrast to higher plant CDKBs that evolved other roles outside cell cycle regulation. This work was supported by the GA CR (grant no. 204/09/0111), the GA AS CR (grant no. IAA500200614) and the Institutional Research Concept (no. AV0Z50200510).
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