Truncated UDP-glucuronosyltransferase (UGT) from a Crigler-Najjar syndrome type II patient colocalizes with intact UGT in the endoplasmic reticulum.

Mutations in the gene encoding bilirubin UDP-glucuronosyltransferase (UGT1A1) are known to cause Crigler-Najjar syndrome type II (CN-II). We previously encountered a patient with a nonsense mutation (Q331X) on one allele and with no other mutations in the promoter region or other exons, and proposed that CN-II is inherited as a dominant trait due to the formation of a heterologous subunit structure comprised of the altered UGT1A1 gene product (UGT1A1-p.Q331X) and the intact UGT1A1.