Five cDNAs Encoding Arabidopsis GF14 Proteins

The transcriptional regulation of gene expression depends to a large degree on the interaction of cis-acting elements and trans-acting factors. The G-box (5’-CCACGTGG-3’) is an important cis-acting element present in the Arabidopsis Adh promoter (McKendree et al., 1990; McKendree and Ferl, 1992). In addition, the G-box motif is also found in the promoter of other environmentally inducible plant genes (Williams et al., 1992), such as genes encoding the Arabidopsis Chl a/b-binding protein, the early Met-labeled polypeptide in wheat, chalcone synthase in parsley, and the small subunit of Rubisco in Arabidopsis and tomato. The G-box binding factor has been demonstrated in a vast array of plants, such as Arabidopsis (McKendree et al., 1990) and maize (De Vetten et al., 1992), and has been cloned from Arabidopsis (Schindler et al., 1992) and other plants (Brunelle and Chua, 1993) by means of G-box oligonucleotide screening. To detect a11 of the components of the G-box-binding complex, monoclonal antibodies against the partially purified G-box-binding protein complex were prepared (Lu et al., 1992). Using one of the monoclonal antibodies (anti-GF14), we have isolated cDNA clones of proteins (termed GF14) that are involved in the G-box-binding complex from maize (De Vetten et al., 1992) and Arabidopsis (Lu et al., 1992). Based on the westem assay, anti-GF14 detects at least five polypeptides in extracts of Arabidopsis plant or suspension cells (Lu et al., 1992), indicating that GF14 is probably a family of proteins. We found another four distinct clones by using the anti-GF14 monoclonal antibody to re-screen the Xgtl 1 cDNA expression library (Clontech, Palo Alto, CA) constructed from Arabidopsis thaliana suspension cell culture mRNA. Positively reacting plaques were purified, and the EcoRI inserts were amplified, cloned, and sequenced on an Applied Biosystems (Foster City, CA) 373A DNA sequencer (Lu et al., 1992). The four additional full-length cDNAs exhibit approximately 60% identity with pLU14 in the coding region at the nucleotide leve1 (Lu et al., 1992) (Table I). To uniquely identify the original GF14 clone and subsequent homologs, a Greek letter designation has been added in keeping with the precedent set in the literature of mammalian homologs of this protein family (Aitken et al., 1992). The original GF14