The high mobility group (HMG) proteins represent a class of chromosomal non-histone proteins with an assumed influence on transcription. In this context, the effect of the maize HMGa protein on reporter gene expression was examined. Transient co-transformation experiments in maize protoplasts with plasmid constructs directing the synthesis of the maize HMGa protein and with a luciferase reporter plasmid demonstrated a stimulatory effect of the HMGa protein on the reporter gene expression. Additional experiments with HMGa deletion constructs indicated that the HMG-Box DNA-binding motif is important for the observed effect, while the acidic carboxy-terminal domain of the HMGa protein appears to be dispensable.
