The transcriptional regulator CPRF1: Expression analysis and gene structure

Many eukaryotic DNA-binding proteins share a conserved amino acid sequence known as the basic region leucine zipper (bZIP) domain. bZIP proteins recognise DNA, upon dimerization, in a sequence-specific manner. The Common Plant Regulatory Factor 1 (CPRF1) is a bZIP transcription factor from parsley (Petroselinum crispum), which recognises defined elements containing ACGT cores. CPRF1 genomic DNA was cloned and the gene was sequenced. Analysis of the sequence data revealed the existence of 12 exons and 11 introns within a stretch of about 9 kb. A second RNA species hybridising to CPRF1 probes was identified as an alternatively spliced, additional CPRF1 transcript containing intron 8. This polyadenylated RNA species showed accumulation characteristics very similar to those of the CPRF1 mRNA. CPRF1 specifically binds an ACGT-containing element which is located within the composite regulatory unit that is necessary and sufficient for light activation of the parsley chalcone synthase (CHS) minimal promoter. Expression studies at the mRNA level demonstrated that CPRF1 mRNA is present in all organs of light-grown plants in which CHS mRNA expression is detectable, and light-dependent CHS mRNA accumulation was shown to be blocked by cycloheximide. Therefore, translation of a protein factor, possibly CPRF1, may be a prerequisite for CHS promoter activation.