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xeroderma pigmentosum, complementation group E (XPE)

Xeroderma pigmentosum is an autosomal recessive pigmentary skin disorder characterized by solar hypersensitivity of the skin, high predisposition for developing cancers on areas exposed to sunlight and, in some cases, neurological abnormalities. Some XP-D patients present features of Cockayne syndrome, including dwarfism, sensorineural deafness, microcephaly, mental retardation, pigmentary retinopathy, ataxia, decreased nerve conduction velocities.

XPE is caused by mutations in the DDB2 gene (600811).
Patients has mild XP symptoms and no neurologic abnormalities. Paients suffer from a skin disease less severe than that seen in patients of several other complementation groups.

Keeney et al. (1993) purified to near homogeneity from HeLa cells a DNA damage-binding protein (DDB1; 600045) implicated in xeroderma pigmentosum E. The protein was abundant and had a native molecular weight of about 160,000 as estimated by gel filtration and glycerol gradient sedimentation. DNA damage binding activity copurified with polypeptides of 124 and 41 kD. It appeared that the 2 polypeptides are subunits of a heterodimeric protein. Keeney et al. (1994) injected purified human DDB protein into XPE cells and showed that DNA repair was stimulated to normal levels in those strains that lacked the DDB activity but not in cells from other xeroderma pigmentosum groups or in the subset of XPE cells that contain the activity. These results provided direct evidence that defective DDB activity causes the repair defect in a subset of XPE patients, which in turn establishes a role for this activity in nucleotide-excision repair in vivo. Thus, there appear to be 2 types of xeroderma pigmentosum, group E: a DDB-positive form and a DDB-negative form. Mutations in the smaller component of the heterodimeric protein, encoded by the DDB2 gene were demonstrated by Nichols et al. (1996) in cases of the DDB-negative form. Nichols et al. (1996) demonstrated mutations in the DDB2 gene, which encodes the p48 subunit of the DDB heterodimer (600811.0001).



TYPE: skin problem

Related patway(s): nucleotide excision repair (NER)

DNAtraffic protein(s) related to disease: DDB2 (XPE)

OMIM: 278740

Last modification date: Aug. 17, 2011