The present invention relates to an isolated human nucleic acid molecule encoding a protein or polypeptide which controls RNA polyadenylation, an isolated mouse nucleic acid molecule encoding a protein or polypeptide which controls RNA polyadenylation, and nucleic acid constructs, host cells and an expression system incorporating the nucleic acid molecules. The present invention also discloses methods of diagnosing male infertility; a method of contraception for mammals; and a method for diagnosing a cancerous condition in a subject using the nucleic acid molecules and proteins of the present invention.