title: A novel mouse Smad4 mutation reduces protein stability and wild-type protein levels.
abstract: Smad4 is a key signal transducer of the transforming growth factor-beta (TGF-beta) superfamily of growth factors that are critical regulators of embryonic patterning and adult tissue homeostasis. The biological activity of the TGF-beta signaling is tightly controlled at multiple levels, including the abundance of SMAD4 proteins. We previously recovered a novel allele of Smad4 in a gene-based screen in N-ethyl-N-nitrosourea (ENU)-mutagenized mouse embryonic stem cells. The mutation resulted in an unstable truncated protein that is degraded through proteasomal pathways. In the heterozygous state, this allele acts in a dominant negative fashion to reduce the wild-type protein level as well as signaling output. Biochemical characterization indicated that the truncated protein is able to form a complex with the wild-type protein, thus targeting it for proteasomal degradation as well. Phenotypic analyses of the heterozygous animals provided insight into the threshold requirement of Smad4-dependent signaling in vivo.
authors.affiliation: Department of Genetics, Carolina Center for Genome Sciences, University of North Carolina at Chapel Hill, 27599, USA.
authors.forename: Yijing
authors.initials: Y
authors.lastname: Chen
authors.forename: Della
authors.initials: D
authors.lastname: Yee
authors.forename: Terry
authors.initials: T
authors.lastname: Magnuson
mesh_terms: D000483:Alleles; D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004622:Embryo, Mammalian / Q000166:cytology; D005799:Genes, Dominant; D006579:Heterozygote; D007976:Leupeptins / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation / Q000235:genetics*; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D010641:Phenotype; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D015398:Signal Transduction; D051901:Smad4 Protein / Q000235:genetics* / Q000378:metabolism; D013234:Stem Cells / Q000187:drug effects / Q000378:metabolism
chemical_list: D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D011500:Protein Synthesis Inhibitors; D051901:Smad4 Protein; C490810:Smad4 protein, mouse; D003513:Cycloheximide; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde