Xeroderma Pigmentosum, Complementation Group D (XPD)

ERCC2, or XPD is a protein involved in transcription-coupled nucleotide excision repair.The XPD (ERCC2) gene encodes for a 2.3-kb mRNA containing 22 exons and 21 introns. The XPD protein is a 760 amino acids polypeptide with a size of 87kDa. Defects in this gene can result in three different disorders: the cancer-prone syndrome xeroderma pigmentosum complementation group D, trichothiodystrophy, and Cockayne syndrome.

Just like XPB, XPD is also a part of human transcriptional initiation factor TFIIH and has ATP-dependent helicase activity. It belongs to the RAD3/XPD subfamily of helicases.XPD is essential for the viability of cells. Deletion of XPD in mice is embryonic lethal.