May act as a regulator of transcription factor IIIA (TFIIIA) gene expression. Efficient DNA binding requires dimerization with another bHLH protein. Binds DNA as a homodimer or a heterodimer. Oocyte and somatic tissue. Oocytic and somatic forms of this protein exist, probably as a result of post-translational modifications or minor splicing differences. In the oocyte, the protein accumulates from stage 1 to stage 5/6 of oogenesis and persists through gastrulation while the somatic protein begins to accumulate at early cleavage and, by the neurula stage, is the dominant, if not exclusive, form present.