Seems to be involved in regulation of transcriptional activity of MYC. In vitro, inhibits DNA-binding activity of Mad-MAX heterodimers. Can recruit Mad transcriptional repressors (MXD1, MXD3, MXD4 and MXI1) to the cytoplasm. May be involved in spermiogenesis (By similarity). Interacts with MXD1, MXD3, MXD4, MXI1 and PIWIL1. Self-associates (By similarity). Predominantly found in the cytoplasm. Component of a nuage in male germ cells (an electron-dense spherical cytoplasmic body present in late pachytene and diplotene spermatocytes and in elonging spermatids) (By similarity). Testis specific.