ANALYSIS OF FRA-2 GENE-EXPRESSION

We have analyzed the transcriptional regulation of the fra-2 gene in c hicken embryo fibroblasts. Like c-fos, fra-2 was inducible by phorbol ester, cAMP and calcium ionophore, as well as serum. In all three case s, the induction of two species of fra-2 transcript (5.7 kb and 6.8 kb ) was delayed and prolonged compared with that of c-fos mRNA. The size difference between the two transcripts was attributable to the hetero geneity of the 3'-end, probably reflecting utilization of different po lyadenylation sites. The major transcriptional start point is located at 30 bp downstream of a TATA-like sequence. In the fra-2 promoter reg ion, which is located in a typical CpG island, enhancer consensus sequ ences such as SCM, SRE, GC boxes and CRE-like sequences were detected upstream of the TATA-like sequence in the same order as that in the 5' -upstream region of the chicken c-fos gene. Fibroblast transfection st udies with a series of promoter deletion constructs positioned upstrea m of bacterial chloramphenicol acetyl-transferase indicated, however, that SRE-like sequence is not the sole responsible element for the ser um induction, and that a minimal fragment containing no SRE-like seque nce is sufficient for this induction. Two typical AP-1 sequences are l ocated between the major transcriptional initiation site and the codin g sequence, and the binding activity of protein complexes to these seq uences was induced by serum.