Germ cell specific Y-box binding protein (YBX2), a germ-cell-specific member of the Y-box family of DNA-/RNA-binding proteins, is a major constituent of messenger ribonucleoprotein particles (mRNPs) and involved in the regulation of the stability and/or translation of germ cell mRNAs. It is proposed to function as a coactivator of transcription in the nucleus and to stabilize and store maternal and paternal mRNAs in the cytoplasm. YBX2 binds to the Y-box consensus promoter element and is expressed in oocytes and testicular germ cells in the stage of spermatogonia to spermatocyte. Recent studies show that deletion of YBX2 leads to the disruption of both spermatogenesis and oogenesis.