NSF Award
0820228
Posttranslational attachment of the ubiquitin-related protein SUMO to other proteins participates in many vital cellular processes including transcription, signaling and maintenance of genome integrity. However, the mechanisms by which SUMO affects its substrates are poorly understood. This project will determine the role(s) of SUMO in controlling the copy number of the 2 micron circle, a selfish DNA element that resides in budding yeast. SUMO pathway mutants accumulate such high copy numbers of 2 micron that it causes cell death. Preliminary data suggest that this effect is caused by an aberrant activity of Flp recombinase, a protein encoded by 2 micron. This results, at least partly, from deficient SUMO attachment to Flp itself. Importantly, Flp sumoylation requires not only SUMO pathway enzymes, but also other features of 2 micron. This suggests that Flp may become sumoylated as a part of its functional cycle at the DNA.<br/><br/>This hypothesis will be tested by a) defining the role of DNA binding in Flp sumoylation and b) determining whether sumoylation targets a specfic subpopulation of Flp for ubiquitin-dependent proteolysis via a SUMO-specific ubiquitin E3 ligase. This research will help solve a basic question in the SUMO field: how can SUMO affect protein function when most substrates are sumoylated at extremely low levels. Interdependency between enzyme activity and sumoylation would explain this observation, as would sumoylation-dependent proteolysis. A second set of experiments will test whether Flp causes abnormal levels of DNA damage in SUMO pathway mutants. The results of these experiments will shed light on the complex role of the SUMO pathway in maintaining genome stability.<br/><br/>One way that biological processes are regulated is via attachment of certain small proteins, including a protein called SUMO, to other proteins. SUMO is essential for cell growth and is involved in almost every major nuclear process, but the means by which SUMO alters the activity of the proteins to which it is attached is not clear. This project will examine how SUMO attachment controls the activity of the Flp protein and should provide insight into how SUMO acts in other crucial processes as well. The investigator has received a Dean's Citation for her commitment to education and through this award she will continue her contributions in that area. Part of this project will be conducted by a graduate student as part of her Ph.D. thesis research, and undergraduate students will participate in this project through a summer research program. Students and postdoctoral researchers performing this work will present their findings at departmental, city-wide, and international meetings and through scientific publications.
