Aurora A Phosphorylation of YY1 during Mitosis Inactivates its DNA Binding Activity.

Successful execution of mitotic cell division requires the tight synchronisation of numerous biochemical pathways. The underlying mechanisms that govern chromosome segregation have been thoroughly investigated. However, the mechanisms that regulate transcription factors in coordination with mitotic progression remain poorly understood. In this report, we identify the transcription factor YY1 as a novel mitotic substrate for the Aurora A kinase, a key regulator of critical mitotic events, like centrosome maturation and spindle formation. Using in vitro kinase assays, we show that Aurora A directly phosphorylates YY1 at serine 365 in the DNA-binding domain. Using a new phospho-specific antibody, we show that YY1 phosphorylation at serine 365 occurs during mitosis, and that this phosphorylation is significantly reduced upon inhibition of Aurora A. Furthermore, we show, using electrophoretic mobility shift and chromatin immunoprecipitation assays, that phosphorylation of YY1 at this site abolishes its DNA binding activity in vitro and in vivo. In conformity with this loss of binding activity, phosphorylated YY1 also loses its transctivation ability as demonstrated by a luciferase reporter assay. These results uncover a novel mechanism that implicates Aurora A in the mitotic inactivation of transcription factors.