Identification of an Unusual MYB-type Transcription Factor That Binds to Promoter of H-Protein of Glycine Decarboxylase

Expression of the H-protein of the mitochondrial glycine decarboxylase (GDC) complex is controlled at the transcriptional level in a light-dependent and tissue-specific manner. We have identified a protein binding site, HPP-1, within the region of the gdcH promoter that appears to control expression of this gene. Gel shift experiments suggested that the HPP-1 site contains a core DNA sequence of the hexameric palindrome, AATATT. An Arabidopsis cDNA coding for a DNA binding protein, HPPBF-1, was cloned that binds to this same HPP-1 site and has a binding requirement for the same AATATT core sequence. HPPBF-1 belongs to a small class of DNA binding factors that includes the initiator binding proteins, IBPl and BPF-1, as well as the telomeric proteins RTBPl and AtTRP1. These factors are unusual in that they contain a single C-terminal MYB-type DNA binding motif. This binding motif contains the same LKDKW DNA interaction region noted in other MYB factors. RNA blot analysis suggested that the mRNA for HPPBF-1 is present in all organs at varying levels.