TY - JOUR
T1 - Oligomerization conditions Mdm2-mediated efficient p53 polyubiquitylation but not its proteasomal degradation
AU - Hjerpe, Roland
AU - Aillet, Fabienne
AU - Lopitz-Otsoa, Fernando
AU - Lang, Valerie
AU - Torres-Ramos, Monica
AU - Farras, Rosa
AU - Hay, Ronald T.
AU - Rodriguez, Manuel S.
PY - 2010/5
Y1 - 2010/5
N2 - In normal cells p53 is maintained at low level through the action of the ubiquitin-proteasome system. As a consequence of p53 transcriptional activity, various regulators of this tumor suppressor are produced, forming a negative feedback loop tightly controlling p53 stability. One of the most prominent is the ubiquitin-ligase Mdm2. Here, we have used a transfer of signals strategy to study the p53 degradation process promoted by Mdm2 in the absence of p53 transcriptional activity. Our results show that in a p53 null background, transcriptionally silent p53-fusions require multiple N- and C-terminal signals to be optimally targeted to proteasomal degradation. As for WT p53, p53-fusions able to form tetramers are polyubiquitylated and optimally degraded by the proteasome. However, p53 molecules unable to oligomerize, show Mdm2-mediated polyubiquitylation deficiency but are still targeted to proteasome degradation in vitro and ex vivo. In the presence of Mdm2, nuclear shuttling of p53 monomeric fusions favours proteasome-dependent degradability but not its polyubiquitylation. In vitro, 265 proteasome fails to drive degradation of OD mutants in the presence of Mdm2, suggesting the contribution of additional cellular factors in this process. All together, our results indicate that Mdm2-mediated proteasome-dependent degradation of polyubiquitylation deficient p53 monomers is mechanistically possible, taking alternative pathways to better achieve their proteolysis. These results support the existence of additional levels to regulate p53 stability and activity acting on individual subunits of the functional tetramer. (C) 2010 Elsevier Ltd. All rights reserved.
AB - In normal cells p53 is maintained at low level through the action of the ubiquitin-proteasome system. As a consequence of p53 transcriptional activity, various regulators of this tumor suppressor are produced, forming a negative feedback loop tightly controlling p53 stability. One of the most prominent is the ubiquitin-ligase Mdm2. Here, we have used a transfer of signals strategy to study the p53 degradation process promoted by Mdm2 in the absence of p53 transcriptional activity. Our results show that in a p53 null background, transcriptionally silent p53-fusions require multiple N- and C-terminal signals to be optimally targeted to proteasomal degradation. As for WT p53, p53-fusions able to form tetramers are polyubiquitylated and optimally degraded by the proteasome. However, p53 molecules unable to oligomerize, show Mdm2-mediated polyubiquitylation deficiency but are still targeted to proteasome degradation in vitro and ex vivo. In the presence of Mdm2, nuclear shuttling of p53 monomeric fusions favours proteasome-dependent degradability but not its polyubiquitylation. In vitro, 265 proteasome fails to drive degradation of OD mutants in the presence of Mdm2, suggesting the contribution of additional cellular factors in this process. All together, our results indicate that Mdm2-mediated proteasome-dependent degradation of polyubiquitylation deficient p53 monomers is mechanistically possible, taking alternative pathways to better achieve their proteolysis. These results support the existence of additional levels to regulate p53 stability and activity acting on individual subunits of the functional tetramer. (C) 2010 Elsevier Ltd. All rights reserved.
KW - p53
KW - Polyubiquitylation
KW - Degradation
KW - Mdm2
KW - Proteasome
KW - TERMINAL DOMAIN
KW - TRANSCRIPTIONAL ACTIVITY
KW - PROTEIN-DEGRADATION
KW - ACTIVATE P53
KW - IN-VIVO
KW - UBIQUITINATION
KW - MDM2
KW - MULTIPLE
KW - IDENTIFICATION
KW - MUTATIONS
U2 - 10.1016/j.biocel.2010.01.010
DO - 10.1016/j.biocel.2010.01.010
M3 - Article
C2 - 20080206
SN - 1357-2725
VL - 42
SP - 725
EP - 735
JO - International Journal of Biochemistry & Cell Biology
JF - International Journal of Biochemistry & Cell Biology
IS - 5
ER -