MYB domain proteins are conserved transcriptional regulators that are found in all eukaryotes. These transcriptional regulators include the widely distributed three MYB repeat proteins (R1R2R3) represented in animals by the c-MYB proto-oncogene and in plants by both the pc-MYB (R1R2R3) and the two MYB repeat proteins (R2R3), the latter of which has expanded dramatically in higher plants. Some residues within the MYB domain have remained conserved in all eukaryotes while others are conserved only in the higher plants R2R3 MYB proteins. Our studies have focused on Cys53, which is found in MYB domains from plants and animals and which must be reduced for DNA-binding and transcriptional activation.
We have also studied a second residue, Cys49, which is present in just the typical plant R2R3 MYB domains. Using the maize P1 regulator of flavonoid biosynthesis as a typical R2R3 MYB domain protein, we established that Cys49 and Cys53 form a disulfide bond in oxidizing conditions, which impairs DNA binding. Mutations of either Cys49 or Cys53 abolish the dependence on a reduced environment for binding to DNA.
Our results suggest that the evolutionary origin of Cys49 within the plants has provided R2R3 MYB domains with a regulatory feature not present in animal MYB domains, highlighting fundamental structural and functional differences between similar DNA-binding domains from plants and animals. Recently we have identified that several monoclonal antibodies that are able to distinguish between the reduced and oxidized forms of the P1 MYB domain. Using these monoclonal antibodies we are trying to establish if these can be used as a tool to probe the REDOX status of the MYB domain in vivo.
back to projects summary
