Itch self-polyubiquitylation occurs through lysine-63 linkages.
Itch, an E3 protein ubiquitin ligase (E3), which belongs to the homologous to E6-AP carboxy terminus (HECT)-type subfamily, catalyzes its own ubiquitylation. The precise nature of Itch-mediated self-modification and its biological outcome are not completely understood. Here, we show that Itch auto-ubiquitylation is an intermolecular reaction generating Lys63-linkages, rather than the Lys48-linked polyubiquitin chains that target proteins for proteasomal degradation. As a result, Itch is a relatively high stable protein, whose levels are not significantly affected by treatment by either proteasome or lysosome inhibitors. Furthermore, we demonstrate that the decay rate of a catalytic inactive Itch mutant, which is devoided of self-ubiquitylating activity, is barely indistinguishable from the one of the wild-type protein. These data definitely establish a nondegradative role for Lys63-linked Itch self-ubiquitylation.
Scialpi
Flavia
F
IDI-IRCCS Biochemistry Laboratory, Department of Experimental Medicine and Biochemical Sciences, University of Rome "Tor Vergata", Via Montpellier 1, 00133 Rome, Italy.
Malatesta
Martina
M
Peschiaroli
Angelo
A
Rossi
Mario
M
Melino
Gerry
G
Bernassola
Francesca
F
D000818:Animals; D002460:Cell Line; D006207:Half-Life; D006801:Humans; D047468:Immunoprecipitation; D008239:Lysine / Q000378:metabolism*; D051379:Mice; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism*; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000378:metabolism*; D054875:Ubiquitination
D012097:Repressor Proteins; D025801:Ubiquitin; C432966:ITCH protein, human; D044767:Ubiquitin-Protein Ligases; D008239:Lysine