Itch/AIP4 associates with and promotes p63 protein degradation.
p63, a protein related to the tumor suppressor p53, is a transcription factor that plays an important role in epidermal differentiation and limb development. The gene has two distinct promoters that allow the formation of proteins that either contain (TA) or lack (DeltaN) a transactivation domain. In addition, alternative splicing at the 3' end generates proteins with different C-termini, denoted alpha, beta and gamma for a total of six isoforms. DeltaNp63alpha isoform is the main isoform expressed at all stages of development, however the relative contribution of individual p63 isoform during ectodermal differentiation and organogenesis is still far from understood. Overexpression of DeltaNp63 led to increased growth of transformed cells in vitro and in vivo while treatment of keratinocytes with ultraviolet irradiation causes downregulation of DeltaNp63 proteins and their corresponding mRNA. The p63 gene locus is often amplified in squamous cell carcinomas while alterations in the relative levels of TA and DeltaNp63 correlate with prognosis in several human cancers suggesting that fine regulation of p63 intracellular levels must be of pivotal importance in controlling cell proliferation, death and differentiation. Despite its relevance little is known on the mechanisms controlling p63 protein levels. Here we show that Itch/AIP4, a HECT E3-ubiquitin ligase, promotes p63 degradation. Using a set of p63 deletion mutants, we have identified a region and two critical lysine residues of p63, associated to human Split-Hand and Foot Malformation-4 (SHFM-4) syndrome, which are involved in the mechanism of Itch-mediated p63 degradation.
Rossi
Mariangela
M
Dipartimento di Biologia Strutturale e Funzionale, Università di Napoli Federico II, Monte S. Angelo, Napoli, Italy.
De Simone
Marco
M
Pollice
Alessandra
A
Santoro
Raffaela
R
La Mantia
Girolama
G
Guerrini
Luisa
L
Calabrò
Viola
V
D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D050761:Cyclin-Dependent Kinase Inhibitor p57 / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005532:Foot Deformities, Congenital / Q000235:genetics; D017930:Genes, Reporter; D006228:Hand Deformities, Congenital / Q000235:genetics; D006801:Humans; D008156:Luciferases; D008239:Lysine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism*; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D015533:Transcriptional Activation; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
D050761:Cyclin-Dependent Kinase Inhibitor p57; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; C115051:TP63 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; D008156:Luciferases; C432966:ITCH protein, human; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; D008239:Lysine