The c-myc oncogene is important in proliferation, differentiation, apoptosis, and malignant transformation. Products of myc oncogenes are transcription factors that bind to the DNA sequence, CACGTG, and regulate the expression of multiple target genes. Several myc target genes include ECA39, p53, ornithine decarboxylase (ODC), alpha-prothymosin, and Cdc25A. There is a high degree of identity among the mouse, human, and yeast ECA39 proteins. The myc recognition binding site of ECA39 is located 3' to the start site of transcription in the mouse and human genes, but this element is absent in the nematode and yeast. Additionally, the tissue specific expression of ECA39 during embryogenesis is similar between human and mouse. Disruption of the ECA39 gene in yeast results in an increased growth rate in comparison to wild type, such that G1 is shorter. Furthermore, ECA39 is expressed in c-myc induced tumors and displays significant homology to the prokaryotic branched-chain amino acid aminotransferase (BCAT). Thus, ECA39 may be involved in the regulation of the cell cycle, possibly at the G1 to S phase transition.