Adenovirus E1A proteins direct subcellular redistribution of Nek9, a NimA-related kinase.

A monoclonal antibody raised against adenovirus EIA-associated cellular proteins recognized Nek9, a NimA-related protein kinase. Subcellular fractionation and immunofluorescence indicated that Nek9 was primarily cytoplasmic with a small portion located in the nucleus whereas E I A was primarily nuclear. Although co-immunoprecipitation experiments indicated that nuclear Nek9 interacted, directly or indirectly, with EIA, the major effect of EIA was to diminish the amount of Nek9 in the nucleus suggesting that EIA alters the subcellular distribution of Nek9 and that the interaction is transient. A Nek9 deletion mutant lacking a central RCC1-like domain interacted stably with E IA and accumulated in the nucleus in the presence of EIA, possibly representing an intermediate stage of the normally transient Nek9/EIA interaction. The interaction of Nek9 with EIA was dependent on the N-terminal sequences of EIA. Attempts to stably overexpress either Nek9 or the kinase-inactive mutant in various cell lines were unsuccessful; however, the presence of E I A allowed stable overexpression of both proteins. These results suggest that E I A disrupts a nuclear function of Nek9.