title: PCAF ubiquitin ligase activity inhibits Hedgehog/Gli1 signaling in p53-dependent response to genotoxic stress.
abstract: The Hedgehog (Hh) signaling regulates tissue development, and its aberrant activation is a leading cause of malignancies, including medulloblastoma (Mb). Hh-dependent tumorigenesis often occurs in synergy with other mechanisms, such as loss of p53, the master regulator of the DNA damage response. To date, little is known about mechanisms connecting DNA-damaging events to morphogen-dependent processes. Here, we show that genotoxic stress triggers a cascade of signals, culminating with inhibition of the activity of Gli1, the final transcriptional effector of Hh signaling. This inhibition is dependent on the p53-mediated elevation of the acetyltransferase p300/CBP-associated factor (PCAF). Notably, we identify PCAF as a novel E3 ubiquitin ligase of Gli1. Indeed PCAF, but not a mutant with a deletion of its ubiquitination domain, represses Hh signaling in response to DNA damage by promoting Gli1 ubiquitination and its proteasome-dependent degradation. Restoring Gli1 levels rescues the growth arrest and apoptosis effect triggered by genotoxic drugs. Consistently, DNA-damaging agents fail to inhibit Gli1 activity in the absence of either p53 or PCAF. Finally, Mb samples from p53-null mice display low levels of PCAF and upregulation of Gli1 in vivo, suggesting PCAF as potential therapeutic target in Hh-dependent tumors. Together, our data define a mechanism of inactivation of a morphogenic signaling in response to genotoxic stress and unveil a p53/PCAF/Gli1 circuitry centered on PCAF that limits Gli1-enhanced mitogenic and prosurvival response.
authors.affiliation: Department of Molecular Medicine, University of Rome La Sapienza, Rome, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Mazzà
authors.forename: P
authors.initials: P
authors.lastname: Infante
authors.forename: V
authors.initials: V
authors.lastname: Colicchia
authors.forename: A
authors.initials: A
authors.lastname: Greco
authors.forename: R
authors.initials: R
authors.lastname: Alfonsi
authors.forename: M
authors.initials: M
authors.lastname: Siler
authors.forename: L
authors.initials: L
authors.lastname: Antonucci
authors.forename: A
authors.initials: A
authors.lastname: Po
authors.forename: E
authors.initials: E
authors.lastname: De Smaele
authors.forename: E
authors.initials: E
authors.lastname: Ferretti
authors.forename: C
authors.initials: C
authors.lastname: Capalbo
authors.forename: D
authors.initials: D
authors.lastname: Bellavia
authors.forename: G
authors.initials: G
authors.lastname: Canettieri
authors.forename: G
authors.initials: G
authors.lastname: Giannini
authors.forename: I
authors.initials: I
authors.lastname: Screpanti
authors.forename: A
authors.initials: A
authors.lastname: Gulino
authors.forename: L
authors.initials: L
authors.lastname: Di Marcotullio
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004249:DNA Damage; D057809:HEK293 Cells; D053823:Hedgehog Proteins / Q000378:metabolism; D006801:Humans; D051741:Kruppel-Like Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008934:Mitogens / Q000494:pharmacology; D008954:Models, Biological; D059748:Proteolysis / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects; D000071676:Zinc Finger Protein GLI1; D050880:p300-CBP Transcription Factors / Q000378:metabolism*; D000099224:p300-CBP-Associated Factor
chemical_list: D053823:Hedgehog Proteins; D051741:Kruppel-Like Transcription Factors; D008934:Mitogens; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D044767:Ubiquitin-Protein Ligases; D000071676:Zinc Finger Protein GLI1; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C400551:GLI1 protein, human; C498520:Gli1 protein, mouse