Tgfbeta signaling directly induces Arf promoter remodeling by a mechanism involving Smads 2/3 and p38 MAPK.

ABSTRACT: We have investigated how the Arf gene product, p19(Arf), is activated by Tgf? during mouse embryo development to better understand how this important tumor suppressor is controlled. Taking advantage of new mouse models, we provide genetic evidence that Arf lies downstream of Tgf? signaling in cells arising from the Wnt1-expressing neural crest and that the anti-proliferative effects of Tgf? depend on Arf in vivo. Tgf?1, -2, and -3 (but not BMP-2, another member of the Tgf? superfamily) induce p19(Arf) expression in wild type mouse embryo fibroblasts (MEFs), and they enhance Arf promoter activity in Arf(lacZ/lacZ) MEFs. Application of chemical inhibitors of Smad-dependent and -independent pathways show that SB431542, a Tgf? type I receptor (T?rI) inhibitor, and SB203580, a p38 MAPK inhibitor, impede Tgf?2 induction of Arf. Genetic studies confirm the findings; transient knockdown of Smad2, Smad3, or p38 MAPK blunt Tgf?2 effects, as does Cre recombinase treatment of Tgfbr2(fl/fl) MEFs to delete Tgf? receptor II. Chromatin immunoprecipitation reveals that Tgf? rapidly induces Smads 2/3 binding and histone H3 acetylation at genomic DNA proximal to Arf exon 1?. This is followed by increased RNA polymerase II binding and progressively increased Arf primary and mature transcripts from 24 through 72 h, indicating that increased transcription contributes to p19(Arf) increase. Last, Arf induction by oncogenic Ras depends on p38 MAPK but is independent of T?rI activation of Smad 2. These findings add to our understanding of how developmental and tumorigenic signals control Arf expression in vivo and in cultured MEFs.

SUBMITTER: Zheng Y 

PROVIDER: S-EPMC2975190 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature