MYCBP, also known as c-Myc binding protein, binds to the transactivation domain of c-Myc and stimulates the activation of E-box-dependent transcription. It translocates from the cytoplasm to the nucleus during S phase when increased expression of c-Myc occurs. It has also been shown to associate with AKAP 149 and AKAP 84 in mitochondria of somatic cells and sperm, which suggests a role for MYCBP in spermatogenesis.