Transcription of fra-2 mRNA and phosphorylation of Fra-2 protein are stimulated by serum.

The RNA transcript and the gene product of a newly isolated fos-related gene, fra-2, were analyzed in growth-arrested and growth-stimulated chicken embryo fibroblasts (CEF). In the growth-arrested cells, a small amount of 6.8 kilobase (kb) fra-2 transcript was synthesized and several species (40-46 kilodaltons (kd) of hypophosphorylated fra-2 gene products (Fra-2) were detected. After the growth stimulation, two species of fra-2 transcripts of 6.8 kb and 5.7 kb were transiently induced. Compared with c-fos mRNA, expression of these fra-2 mRNAs was significantly prolonged, in good agreement with the previous analysis on the synthetic rate of Fos and Fra-2 proteins. Upon growth stimulation, Fra-2 undergoes more extensive phosphorylation on serine residues to form a 46 kd band, possibly owing to the protein kinase activity induced by serum.