RESUMEN
The alpha-subunit of the heterotrimeric G protein G13 regulate cell growth, differentiation and apoptosis in different cell types. Expression of the constitutively activated mutant of G(alpha)13 (G(alpha13)QL) increases the expression of Egr-1, an immediate-early response gene that is identified to be involved in cell growth, differentiation, and apoptosis. Here we report that G(alpha13)QL activates the promoter of Egr-1 through specific sequence which includes the characteristic CArG boxes. We also demonstrate that the G(alpha13)QL activation of Egr-1 promoter is mediated by the Ras-like small GTPase Rho.
Asunto(s)
Proteínas de Unión al ADN/biosíntesis , Proteínas de Unión al GTP/fisiología , Proteínas Inmediatas-Precoces , Factores de Transcripción/biosíntesis , Células 3T3 , Animales , Proteínas de Unión al ADN/genética , Proteína 1 de la Respuesta de Crecimiento Precoz , Inducción Enzimática , Subunidades alfa de la Proteína de Unión al GTP G12-G13 , Proteínas de Unión al GTP/deficiencia , Proteínas de Unión al GTP/genética , Genes Inmediatos-Precoces , Genes Reporteros , Ratones , Regiones Promotoras Genéticas , Proteínas Recombinantes de Fusión/biosíntesis , Transducción de Señal , Factores de Transcripción/genética , Proteínas de Unión al GTP rhoRESUMEN
Expression of the constitutively activated mutant alpha-subunit of the heterotrimeric G protein G alpha 13 (alpha 13Q226L) leads to the transformation of NIH-3T3 cells. An analysis of the mitogenic pathway mediated by alpha 13Q226L indicated that the expression of the primary response genes, early growth response gene-1 (Egr-1, a nuclear transcription factor with zinc-finger motif) and c-fos (a leucine zipper transcription factor as well as a protooncogene) are constitutively activated in alpha 13Q226L-transformants. While ras-transformed cells did not express Egr-1, cells transformed by the GTPase deficient mutant alpha-subunit of G alpha 12 (alpha 12Q229L) exhibited a "weak" expression, suggesting that the induction of Egr-1 and c-fos is intrinsic to G alpha 13 signaling pathway and not a consequence of the transformed phenotype. Taken together, these results provide the first evidence that the G alpha 13 signaling pathway involves the activation of specific transcription factors and defines the expression of these nuclear transcription factors as a possible molecular mechanism in alpha 13Q226L-mediated cell proliferation and transformation.