Involvement of Chlamydomonas DNA damage tolerence gene UBC2 in lipid accumulation

The Lys-63-linked polyubiquitination of target proteins is considered a fundamentally different process from conventional Lys-48-linked polyubiquitination. This process is deemed analogous to other post-translational regulatory processes, such as phosphorylation and sumoylation, which alter target protein activities and are reported to be involved in several cellular processes. In this study, we report that CrUBC2, a yeast and Arabidopsis MMS2/UEV homolog gene in Chlamydomonas reinhardtii, is able to functionally rescue yeast mms2 mutant, leading to increased DNA damage tolerance. The overexpression of the CrUBC2 improves the algal ability to tolerate DNA damage, while silencing CrUBC2 sensitizes cells to DNA damage, indicating that CrUBC2 is involved in DNA-damage response in Chlamydomonas. Moreover, the overexpression of CrUBC2 increases algal cell lipid, while the silencing of CrUBC2 gene decreases lipid content, implying that a protein substrate of CrUBC13-CrUBC2 polyubiquitination is involved in lipid accumulation.