Cell cycle arrest after DNA damage in Chlamydomonas reinhardtii

Mária Čížková1, Monika Hlavová1, Milada Vítová1, James G. Umen2, Kateřina Bišová1, and Vilém Zachleder1

1) Laboratory of Cell Cycles of Algae, Institute of Microbiology, ASCR, Třeboň, Czech Republic 2) Plant Molecular Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, USA

Although cellular genome is relatively stable, it can be altered both spontaneously and after exposition to various DNA damaging agents. Cells usually respond to the genome damage by activating a DNA damage response pathway. We studied the effects of zeocin, a bleomycin family antibiotics causing double stranded breaks, and caffeine, methylxantine synergistic with many DNA damaging agents, on the growth rate, cell survival and cell cycle progression of the alga Chlamydomonas reinhardtii. Chlamydomonas reinhardtii is model unicelullar green alga dividing by multiple fission. Its cell cycle consists of long G1 phase followed by n alternating rounds of S phase and mitosis, terminated by cell division into 2n daughter cells. Increasing concentrations of zeocin severely affected cell survival and blocked nuclear and cell divisions. Moreover, Chlamydomonas cells were hypersensitive to DNA damage if combined with the presence of caffeine. In the presence of caffeine only, the cells divided faster comparing to untreated control, proably due to degradation of inhibitor of mitosis, Wee1. Here, we show that application of caffeine can override a cell cycle arrest following to DNA damage. It implies DNA damage pathway is conserved from algae to higher eukaryotes. This work was supported by the GA CR (grant nos. 204/09/0111, P501/10/P258), the GA AS CR (grant no. IAA500200614) and the Institutional Research Concept (no. AV0Z50200510).

e-mail address of presenting author: maria.cizkova@gmail.com