CYC1 and cancer: For example, human cytochrome c1, whose gene is regulated by E2F [44], participates in an electron transport chain and the mitochondria pathway of apoptosis whereas a similar set of electron transport-related genes (COX8, CYB5-M, CYP51A1, FDXR and SUCLG1) were found to be E2F4-bound in cancer cell lines [45].