TP53INP1s and Homeodomain-interacting Protein Kinase-2 (HIPK2) Are Partners in Regulating p53 Activity

Richard Tomasini,Amina Azizi Samir,Alice Carrier,Daniel Isnardon,Barbara Cecchinelli,Silvia Soddu,Bernard Malissen,Jean-Charles Dagorn,Juan L Iovanna,Nelson J Dusetti

doi:10.1074/jbc.m301979200

Abstract

The TP53INP1 gene encodes two protein isoforms, TP53INP1alpha and TP53INP1beta, located into the nucleus. Their synthesis is increased during cellular stress by p53-mediated activation of transcription. Overexpression of these isoforms induces apoptosis, suggesting an involvement of TP53INP1s in p53-mediated cell death. It was recently shown that p53-dependent apoptosis is promoted by homeodomain-interacting protein kinase-2 (HIPK2), which is known to bind p53 and induce its phosphorylation in promyelocytic leukemia protein nuclear bodies (PML-NBs). In this work we show that TP53INP1s localize with p53, PML-IV, and HIPK2 into the PML-NBs. In addition, we show that TP53INP1s interact physically with HIPK2 and p53. In agreement with these results we demonstrate that TP53INP1s, in association with HIPK2, regulate p53 transcriptional activity on p21, mdm2, pig3, and bax promoters. Furthermore, TP53INP1s overexpression induces G1 arrest and increases p53-mediated apoptosis. Although a TP53INP1s and HIPK2 additive effect was observed on apoptosis, G1 arrest was weaker when HIPK2 was transfected together with TP53INP1. These results indicate that TP53INP1s and HIPK2 could be partners in regulating p53 activity.

Highlights

The stress-induced protein (SIP) gene, recently cloned by Tomasini et al [1], is strongly activated in the diseased pancreas
We found that overexpression of SIP18 or SIP27 induces apoptosis, indicating that SIP gene expression is a key element in p53-mediated cell death that occurs as a consequence of cellular stress
Sequence analysis revealed that SIP, p53DINP1, and TEAP are alternative names for the same gene that was approved as TP53INP1 by the HUGO Gene Nomenclature Committee, with TP53INP1␣ and TP53INP1␤ proteins corresponding to SIP18 and SIP27, respectively

Summary

Introduction

The stress-induced protein (SIP) gene, recently cloned by Tomasini et al [1], is strongly activated in the diseased pancreas. Okamura et al [4] cloned a new human gene named p53DINP1 This gene encodes a p53-inducible nuclear protein that promotes apoptosis when overexpressed in MCF7 cells. Two papers showed that in subnuclear structures called promyelocytic leukemia protein nuclear bodies (PML-NBs), the homeodomain-interacting protein kinase-2 (HIPK2) binds to p53 and phosphorylates its Ser-46 to promote p53-dependent apoptosis [7, 8]. Taken together, these data suggest that HIPK2 could be the kinase that binds to TP53INP1s. The aim of the present work was to investigate a possible relationship between TP53INP1s, HIPK2, and p53

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