Adenovirus E1B 55-kilodalton protein is a p53-SUMO1 E3 ligase that represses p53 and stimulates its nuclear export through interactions with promyelocytic leukemia nuclear bodies.
Oncogenic transformation by adenovirus E1A and E1B-55K requires E1B-55K inhibition of p53 activity to prevent E1A-induced apoptosis. During viral infection, E1B-55K and E4orf6 substitute for the substrate-binding subunits of the host cell cullin 5 class of ubiquitin ligases, resulting in p53 polyubiquitinylation and proteasomal degradation. Here we show that E1B-55K alone also functions as an E3 SUMO1-p53 ligase. Fluorescence microscopy studies showed that E1B-55K alone, in the absence of other viral proteins, causes p53 to colocalize with E1B-55K in promyelocytic leukemia (PML) nuclear bodies, nuclear domains with a high concentration of sumoylated proteins. Photobleaching experiments with live cells revealed that E1B-55K tethering of p53 in PML nuclear bodies decreases the in vivo nuclear mobility of p53 nearly 2 orders of magnitude. E1B-55K-induced p53 sumoylation contributes to maximal inhibition of p53 function since mutation of the major p53 sumoylation site decreases E1B-55K-induced p53 sumoylation, tethering in PML nuclear bodies, and E1B-55K inhibition of p53 activity. Mutation of the E1B-55K sumoylation site greatly inhibits E1B-55K association with PML nuclear bodies and the p53 nuclear export to cytoplasmic aggresomes observed in E1A-E1B-transformed cells. Purified E1B-55K and p53 form high-molecular-weight complexes potentially through the formation of a network of E1B-55K dimers bound to the N termini of p53 tetramers. In support of this model, a p53 mutation that prevents tetramer formation greatly reduces E1B-55K-induced tethering in PML nuclear bodies and p53 nuclear export. These data indicate that E1B-55K's association with PML nuclear bodies inactivates p53 by first sequestering it in PML nuclear bodies and then greatly facilitating its nuclear export.
Pennella
Mario A
MA
Molecular Biology Institute and Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California 90095, USA.
Liu
Yue
Y
Woo
Jennifer L
JL
Kim
Chongwoo A
CA
Berk
Arnold J
AJ
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D017501:Adenovirus E1B Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D019281:Dimerization; D006801:Humans; D045586:Intranuclear Inclusion Bodies / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism*; D038761:Photobleaching; D000071156:Promyelocytic Leukemia Protein; D025842:SUMO-1 Protein / Q000378:metabolism*; D058207:Sumoylation; D014157:Transcription Factors / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
D017501:Adenovirus E1B Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D025842:SUMO-1 Protein; C495501:SUMO1 protein, human; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C070576:PML protein, human; D044767:Ubiquitin-Protein Ligases