Stayton et al. (1994) described the cloning and characterization of a gene, provisionally called X-linked helicase-2 (XH2), located on chromosome Xq13. The gene undergoes X inactivation, contains a 4-kb open reading frame, and encodes a putative NTP-binding nuclear protein homologous to several members of the helicase II superfamily. In situ hybridization studies in the mouse revealed precocious, widespread expression of the murine homolog of XH2 at early stages of embryogenesis, and more restricted expression during late developmental stages and at birth. XH2 shares 6 conserved, collinear domains with other members of the family of proven and putative helicases. In particular, the XH2 protein shows homology with RAD54. Type II helicases have been implicated in nucleotide excision repair and initiation of transcription.