AuroraB-kinase methylation by SETD6 regulates cytokinesis and protects cells from chromosomal instability

SETD6 is a non-histone lysine methylatransferase, previously shown to participate in several housekeeping signaling pathways such as the NFkB pathway, Wnt signaling pathway, mitosis and more. In the current study we show evidence that SETD6 methylation is involved in the regulation of cytokinesis - the final process that divides cell contents into two daughter cells. SETD6 depleted HeLa cells presented high levels of chromatin bridges and actin patches, which are commonly observed following chromosomal segregation errors. In a proteomic screen we identified Aurora-B as a novel SETD6 substrate. Aurora-B kinase is an essential regulator of cytokinesis, known to actively delay cytokinesis as a response to the presence of chromatin in the midzone. We found that SETD6 binds and methylates Aurora-B on two adjacent lysine residues. Upon replication stress, Aurora-B methylation by SETD6 increases but is abolished when the two lysine methylation targets are substituted. In addition, replication stress led to a high tendency of SETD6 depleted cells to multinucleate, a major chromosomal-instability (CIN) phenotype. We detected a significant reduction in the Aurora-B kinase activity during cytokinesis in SETD6 knockout cells upon replication stress, which could be the mechanism underlying the accumulation of CIN phenotypes in these cells. CIN is a hallmark of cancer and is associated with tumor cell malignancy. Our findings suggest that Aurora-B methylation by SETD6 carries meaningful implications on tumorigenic cellular pathways.