Characterization of an enhancer-like structure in the promoter region of the proliferating cell nuclear antigen (PCNA) gene.

The steady-state mRNA levels of the proliferating cell nuclear antigen (PCNA) gene depend on the length of its promoter. A promoter extending from the HpaII restriction site at -210 from the cap site to the cap site itself is very active, while a -45 promoter (AatII restriction site) is very weak. We now show that the sequences between -73 and -45 of the human PCNA promoter contain an enhancer-like sequence that markedly increases the levels of PCNA mRNA. This sequence has characteristics of an enhancer, having an enhancing function also when placed away from the native position in the 5' flanking sequence. The increase in mRNA levels that occurs after serum stimulation, however, is independent of the enhancer. Synthetic promoters were also constructed containing mutations in the -73 to -45 sequence and these mutants completely lost their ability to drive the transcription of a heterologous cDNA. Nuclear proteins were shown to bind to this sequence, both by gel shift and by methylation interference analysis. We conclude that the levels of PCNA mRNA are controlled, in part, by a structure located in the 5' flanking sequence of the gene, but that this enhancer-like structure does not play a role in the serum regulation of the mRNA levels.