title: Proteasome-dependent and -independent mechanisms for FosB destabilization: identification of FosB degron domains and implications for DeltaFosB stability.
abstract: The transcription factor DeltaFosB (Delta FosB) accumulates in a region-specific manner in the brain during chronic exposure to stress, drugs of abuse or other chronic stimuli. Once induced, DeltaFosB persists in the brain for at least several weeks following cessation of the chronic stimulus. The biochemical basis of the persistent expression of DeltaFosB has remained unknown. Here, we show that the FosB C-terminus, absent in DeltaFosB as a result of alternative splicing, contains two degron domains. Pulse-chase experiments of C-terminal truncation mutants of full-length FosB indicate that removal of its most C-terminal degron increases its half-life approximately fourfold, and prevents its proteasome-mediated degradation and ubiquitylation, properties similar to DeltaFosB. In addition, removal of a second degron domain, which generates DeltaFosB, further stabilizes FosB approximately twofold, but in a proteasome-independent manner. These data indicate that alternative splicing specifically removes two destabilizing elements from FosB in order to generate a longer-lived transcription factor, DeltaFosB, in response to chronic perturbations to the brain.
authors.affiliation: Department of Psychiatry and Center for Basic Neuroscience, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, Texas, 75390-9070, USA.
authors.forename: Tiffany L
authors.initials: TL
authors.lastname: Carle
authors.forename: Yoshinori N
authors.initials: YN
authors.lastname: Ohnishi
authors.forename: Yoko H
authors.initials: YH
authors.lastname: Ohnishi
authors.forename: Imran N
authors.initials: IN
authors.lastname: Alibhai
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Wilkinson
authors.forename: Arvind
authors.initials: A
authors.lastname: Kumar
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Nestler
mesh_terms: D017398:Alternative Splicing / Q000235:genetics*; D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000503:physiopathology; D005786:Gene Expression Regulation / Q000502:physiology; D016716:PC12 Cells; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D016760:Proto-Oncogene Proteins c-fos / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D013312:Stress, Physiological / Q000378:metabolism* / Q000503:physiopathology
chemical_list: C483820:Fosb protein, rat; D010455:Peptides; D020033:Protein Isoforms; D016760:Proto-Oncogene Proteins c-fos; D046988:Proteasome Endopeptidase Complex