The stomatin-like protein SLP-1 and Cdk2 interact with the F-Box protein Fbw7-γ.
Control of cellular proliferation is critical to cell viability. The F-box protein Fbw7 (hAgo/hCdc4/FBXW7) functions as a specificity factor for the Skp1-Cul1-F-box protein (SCF) ubiquitin ligase complex and targets several proteins required for cellular proliferation for ubiquitin-mediated destruction. Fbw7 exists as three splice variants but the mechanistic role of each is not entirely clear. We examined the regulation of the Fbw7-γ isoform, which has been implicated in the degradation of c-Myc. We show here that Fbw7-γ is an unstable protein and that its turnover is proteasome-dependent in transformed cells. Using a two-hybrid screen, we identified a novel interaction partner, SLP-1, which binds the N-terminal domain of Fbw7-γ. Overexpression of SLP-1 inhibits the degradation of Fbw7-γ, suggesting that this interaction can happen in vivo. When Fbw7-γ is stabilized by overexpression of SLP-1, c-Myc protein abundance decreases, suggesting that the SCF(Fbw7-γ) complex maintains activity. We demonstrate that Cdk2 also binds the N-terminal domain of Fbw7-γ as well as SLP-1. Interestingly, co-expression of Cdk2 and SLP-1 does not inhibit Fbw7-γ degradation, suggesting that Cdk2 and SLP-1 may have opposing functions.
Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota, USA.
Wei
W
Zhang
Elizabeth M
EM
MacDonald
Deanna M
DM
Koepp
D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism*; D044783:F-Box Proteins / Q000737:chemistry / Q000378:metabolism*; D000073979:F-Box-WD Repeat-Containing Protein 7; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000378:metabolism*
D018797:Cell Cycle Proteins; D044783:F-Box Proteins; D000073979:F-Box-WD Repeat-Containing Protein 7; C513273:FBXW7 protein, human; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C117201:STOML1 protein, human; D044767:Ubiquitin-Protein Ligases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D046988:Proteasome Endopeptidase Complex