Cell Cycle Regulation of Igo2 in Budding Yeast

A better explanation of the conserved signaling pathways that coordinate cell growth and cell division is fundamental to understanding and possibly treating cancer.  Recently, the Xenopus protein a-endosulfine (Ensa) has been shown to be essential in controlling mitotic entry by regulating the activity of the phosphatase PP2A-Cdc55. This interaction has been shown to be dependent on the phosphorylation state of Ensa.  Little is known about the budding yeast homologue of Ensa, called Igo2. Specifically we want to address how the phosphorylation state of Igo2 is regulated during the cell cycle and what kinases are responsible for phosphorylating Igo2.  In order to obtain a better understanding, we will construct strains where Igo2 is tagged on its C-terminus with either three copies of the HA epitope (3xHA) or glutathione S-transferase (GST). Using antibodies against these tags, we will be able to monitor post-translational modifications of Igo2 during the cell cycle by western blotting.   Alteration of the kinases that potentially phosphorylate Igo2 will reveal, whether or not they stimulate Igo2.  Igo2 could be part of the pathway that starts mitosis if it becomes phosphorylated during the G2/M checkpoint. The elucidation of Igo2’s activation and function will further improve our knowledge of the signaling pathways that regulate cell growth and division.