The human protein kinase HIPK2 phosphorylates and downregulates the methyl-binding transcription factor ZBTB4

Abstract

HIPK2 is a eukaryotic Serine-Threonine kinase that controls cellular proliferation and survival in response to exogenous signals. Here, we show that the human transcription factor ZBTB4 is a new target of HIPK2. The two proteins interact in vitro, colocalize and associate in vivo, and HIPK2 phosphorylates several conserved residues of ZBTB4. Overexpressing HIPK2 causes the degradation of ZBTB4, whereas overexpressing a kinasedeficient mutant of HIPK2 has no effect. The chemical activation of HIPK2 also decreases the amount of ZBTB4 in cells. Conversely, the inhibition of HIPK2 by drugs or by RNA interference causes a large increase in ZBTB4 levels. This negative regulation of ZBTB4 by HIPK2 occurs under normal conditions of cell growth. In addition, the degradation is increased by DNA damage. These findings have two consequences. First, we have recently shown that ZBTB4 inhibits the transcription of p21. Therefore, the activation of p21 by HIPK2 is twopronged: stimulation of the activator p53, and simultaneous repression of the inhibitor ZBTB4. Second, ZBTB4 is also known to bind methylated DNA and repress methylated sequences. Consequently, our findings raise the possibility that HIPK2 might influence the epigenetic regulation of gene expression at loci that remain to be identified.

Homeodomain-interacting protein kinase 2 plays an important role in normal terminal erythroid differentiation

“…These findings are consistent with other studies implicating the role of Hipk2 in regulation of cell survival and proliferation 7,11,14,18,22 but are the first involving erythropoiesis specifically.…”

HIPK2 phosphorylates ΔNp63α and promotes its degradation in response to DNA damage

“…The HIPK2 activity on DNp63a we are reporting here is consistent with the general idea that the cellular amount of this p63 isoform has to be reduced to enable an effective DDR. A phosphorylation-dependent prodegradation function of HIPK2 has already been reported for CtBP, c-Myb and ZBTB4 (Zhang et al, 2003;Kanei-Ishii et al, 2004;Yamada et al, 2009), suggesting that it might be a common mechanism to destabilize prosurvival factors. Puzzling, the HIPK2 kinase activity is required for the apoptosis-specific activation of p53.…”

MBD4 cooperates with DNMT1 to mediate methyl-DNA repression and protects mammalian cells from oxidative stress

“…Cell extracts were prepared as previously described 33 and resolved on NuPage pre-cast SDS-PAGE gels (Invitrogen) and transferred to Immobilon-P membranes (Millipore). The membranes were blocked with 5% fat-free milk in PBS, then incubated overnight at 4 °C with the appropriate primary antibodies.…”