THE TRANSCRIPTIONAL REGULATOR CPRF1 - EXPRESSION ANALYSIS AND GENE STRUCTURE

Many eukaryotic DNA-binding proteins share a conserved amino acid sequ ence known as the basic region leucine zipper (bZIP) domain. bZIP prot eins recognise DNA, upon dimerization, in a sequence-specific manner. The Common Plant Regulatory Factor 1 (CPRF1) is a bZIP transcription f actor from parsley (Petroselinum crispum), which recognises defined el ements containing ACGT cores. CPRF1 genomic DNA was cloned and the gen e 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 RN A species hybridising to CPRF1 probes was identified as an alternative ly spliced, additional CPRF1 transcript containing intron 8. This poly adenylated RNA species showed accumulation characteristics very simila r to those of the CPRF1 mRNA. CPRF1 specifically binds an ACGT-contain ing element which is located within the composite regulatory unit that is necessary and sufficient for light activation of the parsley chalc one synthase (CHS) minimal promoter. Expression studies at the mRNA le vel demonstrated that CPRF1 mRNA is present in all organs of light-gro wn plants in which CHS mRNA expression is detectable, and light-depend ent CHS mRNA accumulation was shown to be blocked by cycloheximide. Th erefore, translation of a protein factor, possibly CPRF1, may be a pre requisite for CHS promoter activation.