Genome instability is a major driving force behind the development and progression of cancer therefore the mechanisms that prevent genome instability are crucial to help prevent cancer. In addition, many cancer treatments exploit cancer cells’ inability to respond normally to genome instability resulting in cell death. It is therefore vitally important to understand the cellular mechanisms for maintaining genome stability. Here we investigated the role of NSMCE1, a component of the SMC5/6 complex, which is important for several aspects of genome stability maintenance. We used mutant NSMCE1 cell lines to investigate the role of NSMCE1 in SMC5/6 complex formation using immunoprecipitation and western blot analysis. We explored the importance of NSMCE1 for cell cycle progression and genome stability using flow cytometry and DNA damage assays, as well as exploring the ubiquitin modification of NSMCE1 by purification of ubiquitin-modified proteins following formation of epitope-tagged ubiquitin in cells. Our results confirm that NSMCE1 is integral to the formation of the SMC5/6 complex and that it is also essential for cell proliferation. We have demonstrated that a functional NSMCE1 RING domain is not required for SMC5/6 complex formation but is necessary for normal cell growth and division.