Dual Role of SUMO-modification in the function of Homeodomain-inetracting protein kinase 2

다국어 초록 (Multilingual Abstract)

Sumoylation and ubiquitination are major post-translational modification system along with phosphorylation, and play an important role in the regulation of cellular protein function. Homeodomain-interacting protein klinase 2(HIPK2) interacts with and phosphorylates a variety of transcription factors including homeoproteins, Groucho, Myb and p53 that are critical regulators of cell fate decisions and apoptosis during development. Here we show that lysine 25 of HIPK2 is the major sumoylation site, both in vitro and in vivo, and that the sumoylation of this site occurs in a phosphorylation-dependent manner. The sumoylation of HIPK2 had no effect on its catalytic activity but did result in the disruption of its interaction with Groucho corepressor. Consequently, sumoylation inhibited the regulatory activity of HIPK2 on the Groucho-mediated repression of transcription. However, the sumoylation of HIPK2 had no effect on p53 binding or p53-mediated transactivation. These findings indicate a novel regulatory mechanism, by which the phosphorylation-dependent sumoylation of HIPK2 differentiates its binding partner to regulate different target gene transcription upon cellular signaling pathway. HIPK2 is a UV-activated Serine/Threonine protein kinase that phosphorylates p53 on serine 46 and partially colocalizes with p53 on PML-NBs. We also demonstrated that HIPK2 can be modifiedbySUMO-1 at lysine 966, and interact with SUMO-modified PML-IV. Both SUMO-modification and SUMO-interaction of HIPK2 via SUMO-interaction motif were required for its interaction with PML-IV. SUMO-modification of HIPK2 may play a role in PML-NB dynamics during cell cycle and other events that are known to cause alterations to PML-NB structures.