Discovery Of Paralog-Specific Sumo1 And Sumo2 Functions Using Human Cancer Knockout Cells

Small ubiquitin-related modifiers (SUMOs) are ∼100-amino acid polypeptides that function as posttranslational protein modifications and thereby regulate many essential cellular processes, many of which are relevant to cancer. Vertebrates express five SUMO paralogs (SUMO1-5), of which, SUMO1 and SUMO2 are the most widely studied. Biochemical and in vivo studies suggest that SUMO1 and SUMO2 have non-redundant functions, however, the full range of their distinct activities are not fully understood. Understanding these unqiue functions and their molecular bases could lead to more precise therapeutic interventions that target the SUMO pathway. To help define SUMO paralog-specific functions, we used CRISPR-Cas9 to knockout (KO) individual SUMO genes in osteosarcoma U2OS cells. We observed that SUMO2 KO cells were unique in exhibiting a change in cell morphology, changing from epithelial-like to fibroblast-like, thus revealing a potential role for SUMO2 in affecting cell shape. To test the hypothesis that the observed change in morphology is driven in part by changes in gene expression, we sequenced the transcriptome of the parental and SUMO KO cell lines. In alignment with the observed change in SUMO2 KO cell shape, differentially expressed genes (DEGs) involved in the extracellular matrix, basement membrane and epithelial to mesenchymal transition were uniquely enriched in SUMO2 KO cells. Further consistent with SUMO1 and SUMO2 having unique effects on transcription, we found a significantly greater number of unique DEGs in SUMO2 KO cells as compared to SUMO1 KO cells. Furthermore, an overwhelming number of DEGs were down-regulated in the SUMO1 KO cells, suggesting a specific role for SUMO1 in activating, or maintaining, gene expression. In contrast, DEGs in SUMO2 KOs were equally up and down regulated. Collectively, our findings demonstrate that SUMO1 and SUMO2 have unique biological roles and we look forward to better characterizing these paralog-specific functions in future studies. Citation Format: Danielle Bouchard, Wei-Chih Yang, Michael J. Matunis. Discovery of paralog-specific SUMO1 and SUMO2 functions using human cancer knockout cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4877.