The promoter of the human proliferating cell nuclear antigen (PCNA) gene is bidirectional

The proliferating cell nuclear antigen (PCNA) gene codes for a protein that is necessary for cellular DNA synthesis and cell cycle progression. A functional promoter has been identified in the 5′ flanking region of the human PCNA gene. An abbreviated promoter (from the capsite to the PvuII restriction site at -395) was found to be equally efficient in directing transcription from a linked reporter, whether placed in the correct or reverse orientation in respect to the coding sequence. The reporter used was a cDNA of human thymidine kinase (TK), and the bidirectionality of the promoter was demonstrated by its ability to confer the TK⁺ phenotype to TK^-ts13 cells and by the amount of specific message in RNA blots. The PvuII promoter placed between two coding sequences (the TK cDNA and the bacterial gene for neoresistance) is capable of driving transcription simultaneously in both directions. Finally, in blots of RNA from human cells, two transcripts could be detected that hybridized to a sense riboprobe from the 5′ flanking region of the human PCNA gene. We conclude that the locus for the human PCNA gene contains a bidirectional promoter producing diverging transcripts.