title: Merlin/NF2 functions upstream of the nuclear E3 ubiquitin ligase CRL4DCAF1 to suppress oncogenic gene expression.
abstract: Integrin-mediated activation of PAK (p21-activated kinase) causes phosphorylation and inactivation of the FERM (4.1, ezrin, radixin, moesin) domain-containing protein Merlin, which is encoded by the NF2 (neurofibromatosis type 2) tumor suppressor gene. Conversely, cadherin engagement inactivates PAK, thus leading to accumulation of unphosphorylated Merlin. Current models imply that Merlin inhibits cell proliferation by inhibiting mitogenic signaling at or near the plasma membrane. We have recently shown that the unphosphorylated, growth-inhibiting form of Merlin accumulates in the nucleus and binds to the E3 ubiquitin ligase CRL4(DCAF1) to suppress its activity. Depletion of DCAF1 blocks the hyperproliferation caused by inactivation of Merlin. Conversely, expression of a Merlin-insensitive DCAF1 mutant counteracts the antimitogenic effect of Merlin. Expression of Merlin or silencing of DCAF1 in Nf2-deficient cells induce an overlapping, tumor-suppressive program of gene expression. Mutations present in some tumors from NF2 patients disrupt Merlin's ability to interact with or inhibit CRL4(DCAF1). Lastly, depletion of DCAF1 inhibits the hyperproliferation of Schwannoma cells isolated from NF2 patients and suppresses the oncogenic potential of Merlin-deficient tumor cell lines. Current studies are aimed at identifying the substrates and mechanism of action of CRL4(DCAF1) and examining its role in NF2-dependent tumorigenesis in mouse models. We propose that Merlin mediates contact inhibition and suppresses tumorigenesis by translocating to the nucleus to inhibit CRL4(DCAF1).
authors: Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
authors: Jonathan
authors: J
authors: Cooper
authors: Wei
authors: W
authors: Li
authors: Liru
authors: L
authors: You
authors: Gaia
authors: G
authors: Schiavon
authors: Angela
authors: A
authors: Pepe-Caprio
authors: Lu
authors: L
authors: Zhou
authors: Ryohei
authors: R
authors: Ishii
authors: Marco
authors: M
authors: Giovannini
authors: C Oliver
authors: CO
authors: Hanemann
authors: Stephen B
authors: SB
authors: Long
authors: Hediye
authors: H
authors: Erdjument-Bromage
authors: Pengbo
authors: P
authors: Zhou
authors: Paul
authors: P
authors: Tempst
authors: Filippo G
authors: FG
authors: Giancotti
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology*; D005786:Gene Expression Regulation / Q000502:physiology*; D051379:Mice; D025581:Neurofibromin 2 / Q000502:physiology*; D009857:Oncogenes; D010766:Phosphorylation; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases / Q000502:physiology*
chemical_list: D025581:Neurofibromin 2; D044767:Ubiquitin-Protein Ligases