Modification of Drosophila p53 by SUMO Modulates Its Transactivation and Pro-apoptotic Functions

Laura M. McNamee,Federico Mauri,Giannino Del Sal,Licio Collavin,Andrea Lunardi,Michael H. Brodsky,Fulvio Chiacchiera

doi:10.1074/jbc.m710186200

Abstract

Conjugation to SUMO is a reversible post-translational modification that regulates several transcription factors involved in cell proliferation, differentiation, and disease. The p53 tumor suppressor can be modified by SUMO-1 in mammalian cells, but the functional consequences of this modification are unclear. Here, we demonstrate that the Drosophila homolog of human p53 can be efficiently sumoylated in insect cells. We identify two lysine residues involved in SUMO attachment, one at the C terminus, between the DNA binding and oligomerization domains, and one at the N terminus of the protein. We find that sumoylation helps recruit Drosophila p53 to nuclear dot-like structures that can be marked by human PML and the Drosophila homologue of Daxx. We demonstrate that mutation of both sumoylation sites dramatically reduces the transcriptional activity of p53 and its ability to induce apoptosis in transgenic flies, providing in vivo evidence that sumoylation is critical for Drosophila p53 function.

Highlights

SUMO-1 belongs to a family of small ubiquitin-related proteins that are covalently linked to lysine residues of protein substrates [7, 8]
We demonstrate that mutation of both sumoylation sites dramatically reduces the transcriptional activity of p53 and its ability to induce apoptosis in transgenic flies, providing in vivo evidence that sumoylation is critical for Drosophila p53 function
Two knock-in mouse models have been generated in which all C-terminal lysine residues in p53 have been mutated, including the sumoylation site; despite extensive cell culture data indicating critical roles of these residues for p53 function, these mice are similar to wild type, and MEFs and thymocytes derived from these animals display normal apoptotic responses after DNA damage [19, 20]

Summary

Introduction

SUMO-1 belongs to a family of small ubiquitin-related proteins that are covalently linked to lysine residues of protein substrates [7, 8]. When co-transfected with GFP-dSUMO, wild-type p53 and single lysine mutants co-localize with SUMO in nuclear dots. At the higher p53 expression levels, the resulting proteins (p53 K26R and p53 K302R) display a sin- endogenous SUMO accumulates in nuclear dots with wild type, gle slower migrating band (Fig. 1B).

Results

Conclusion