p21 ras as a governor of global gene expression

The molecular mechanisms for signaling by receptor serine/threonine kinases are incompletely understood. To test the potential involvement of p21 H-Ras proteins in signal transduction for type β transforming growth factors (TGFβ), TGFβ-responsive and constitutive reporter genes were cotransfected into cardiac myocytes and mink lung epithelial cells, with dominant inhibitory (Asn-17) or activated (Arg-12) Ras expression vectors. Asn-17 Ras inhibited both TGFβ-dependent and basal expression of inducible promoters (skeletal α-actin and plasminogen activator inhibitor-1), with equivalent dose-response relations. All seven reporter constructs were comparably sensitive to down-regulation by Asn-17 Ras, including those driven by nominally constitutive viral control regions or a TATA-less initiator element. All constructs were up-regulated by Arg-12 Ras more variably. Wild- type Ras had intermediate effects and could rescue a minimal thymidine kinase promoter from inhibition by dominant negative Ras. Thus, a Ras-dependent event is required for efficient expression of an unexpectedly global or inclusive set of genes.