Physical Geography and Sciences



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Lila Toczek, Brianna Gawronski and Michael Ciepluch, Jr., BIO 495: Special Project-SUMO Chain Signals
Faculty Mentor: Professor Xiang-Dong Zhang, Biology

Small ubiquitin-related modifier proteins (SUMOs) are reversibly conjugated to various protein substrates and regulate many different cellular processes including DNA damage repair, ubiquitin-dependent proteolysis, and the cell cycle progression. SUMOylation represents an essential mechanism in control of target proteins’ activity, stability, and interaction with other protein molecules. Among three SUMO paralogs expressed in mammalian cells, SUMO2 and SUMO3 are 96% identical (thereby referred as SUMO2/3), but their identity to SUMO-1 is less than 50%. In contrast to modification of protein targets largely by monomeric SUMO1 in vivo, SUMO2/3 are attached to protein targets in forms of both monomeric SUMO2/3 and polymeric SUMO2/3 chains. Although SUMO2/3-specific antibodies are able to detect both monomeric SUMO2/3 and polymeric SUMO2/3 chain signals, rather than SUMO1 signals, on their target proteins using immunofluorescence microcopy, no approach is currently available to monitor the polymeric SUMO2/3 chain signals in vivo. Here, we developed a novel approach for analyzing polymeric SUMO2/3 chain signals by transfecting cells with the DNA construct encoding GFP-tagged four tandem SUMO-interacting motifs (SIMs), which display a specific high-binding affinity to polymeric SUMO2/3 chain signals, instead of monomeric SUMO-2/3 signals, followed by analysis of the transfected cells using immunofluorescence microscopy. We demonstrated that GFP-SIMs detects polymeric SUMO2/3 chain signals largely concentrated at the midbody of the intercellular bridge in cytokinetic cells with a defect in resolution of the chromosome bridge. Particularly, we elucidated that the polymeric SUMO2/3 chain signals are present in the central section of the midbody, called Flemming body, using the antibodies specifically recognizing the different midbody proteins, including ANCHR, Vps4, Aurora B kinase, phosphorylated Aurora B kinase at Threonine 232, and Plk1 kinase.

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Effects of SUMO Chain Signaling on Mitosis
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