Abstract (eng)
SUMOylation (Small Ubiquitin-related MOdifier) is a post-translational protein modification that can alter the sub-cellular localization, the activity or the interaction partners of proteins. Thus, this reversible modification has been associated with many important cellular processes and the number of newly identified SUMO substrates is steadily increasing. Several chromatin modifying enzymes are modified by SUMO – many of which are responsible to set and to maintain repressive Histone and DNA methylation characteristic for silent heterochromatin. The essential tri-enzymatic SUMO cascade comprises a single E1, a single E2 and several E3 enzymes. The E2 enzyme Ubc9 was found to be deregulated in cancer and is associated with metastasis, tumor cell invasion and resistance to chemotherapy. This study aims to investigate the consequences of Ubc9 deregulation on chromatin in NIH 3T3 mouse fibroblasts. Therefore, the Histone lysine methylation at H3K9 and H4K20, which are characteristic for pericentromeric heterochromatic regions, were investigated. Thereby, Ubc9-siRNA treatments of cells lead to growth arrest and an increase in H4K20 methylation. In contrast to that, no change was observed for the other prominent repressive histone mark, the H3K9 tri-methylation.