Coagulation Factor VIII Associated Protein 1 (F8A1)

F8A is repeated twice extragenically closer to the Xq telomere. This gene is conserved in the mouse implies it has some function. Unlike factor VIII, this gene is transcribed abundantly in a wide variety of cell types.the protein that is mutant in Huntington disease, copurifies with a single novel 40-kD protein termed HAP40. They showed that HAP40 is encoded by the open reading frame F8A gene located within intron 22 of the factor VIII gene. Recombinant HAP40 is cytoplasmic in the presence of huntingtin but is actively targeted to the nucleus in the absence of huntingtin. These data indicated that HAP40 is likely to contribute to the function of normal huntingtin and is a candidate for involvement in the aberrant nuclear localization of mutant huntingtin found in degenerating neurons in Huntington disease.