Differential potency and trans-activation of normal and mutant T24 human H-ras1 gene promoters

Cloning and characterization of the Dictyostelium discoideum rasG genomic sequences

A Dictyostelium discoideum genomic DNA clone containing the ras-related gene, rasG was isolated using the rasG cDNA as a probe. The genomic clone encompasses the entire coding region of the gene and 1.5 kb of 5' flanking region. The rasG gene contains a single intron as determined by sequence comparison with the cDNA, whereas the highly related rasD gene contains three introns. Primer extension analysis showed that transcription of the rasG gene initiates at multiple sites. Sequence analysis of the 5' flanking region of the gene revealed a stretch of thymine residues upstream from the transcription start sites but there is no evidence for a TATA box sequence.

Phorbol ester-responsive H-ras1 gene promoter contains multiple TPA-inducible/AP-1-binding consensus sequence elements

We have constructed recombinant DNA plasmids which carry both the aminoglycoside phosphotransferase (aph) gene and the chloramphenicol acetyl-transferase (CAT) gene linked to the human normal or mutant T24 H-ras1 promoter. We have transfected these plasmids into rat 208F fibroblasts using the calcium phosphate technique and selected for stable transformants by geneticin resistance. These transformants expressed CAT activity at low levels. However, when treated with the phorbol ester TPA, CAT levels increased substantially. Cells transfected with recombinant plasmids carrying a promoterless CAT gene did not respond to TPA. We have noted four motifs in the H-ras1 promoter region which resemble TPA-inducible and AP-1-binding consensus sequences. We suggest that AP-1-like proteins may play a role in control of H-ras1 transcription.