Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutations in the human XPD gene result in a defect in nucleotide excision repair of ultraviolet damaged DNA and cause the cancer-prone syndrome xeroderma pigmentosum (XP). Besides XP, mutations in XPD can cause another seemingly unrelated syndrome, trichothiodystrophy (TTD), characterized by sulfur-deficient brittle hair, ichthyosis, and physical and mental retardation. To ascertain the underlying defect responsible for TTD, we have expressed the TTD mutant proteins in the yeast Saccharomyces cerevisiae and determined if these mutations can rescue the inviability of a rad3 null mutation. RAD3, the S. cerevisiae counterpart of XPD, is required for nucleotide excision repair and also has an essential role in RNA polymerase II transcription. Expression of the wild type XPD protein or the XPD Arg-48 protein carrying a mutation in the DNA helicase domain restores viability to the rad3 null mutation. Interestingly, the XPD variants containing TTD mutations fail to complement the lethality of the rad3 null mutation, strongly suggesting that TTD mutations impair the ability of XPD protein to function normally in RNA polymerase II transcription. From our studies, we conclude that XPD DNA helicase activity is not essential for transcription and infer that TTD mutations in XPD result in a defect in transcription.
 ...
PMID:Lethality in yeast of trichothiodystrophy (TTD) mutations in the human xeroderma pigmentosum group D gene. Implications for transcriptional defect in TTD. 762 61

The skin-cancer-prone hereditary disease xeroderma pigmentosum is typically characterized by defective nucleotide excision repair (NER) of DNA. However, since all subunits of the core basal transcription factor TFIIH are required for both RNA polymerase II basal transcription and NER, some mutations affecting genes that encode TFIIH subunits can result in clinical phenotypes associated with defective basal transcription. Among these is a syndrome called trichothiodystrophy (TTD) in which the prominent features are brittle hair and nails, and dry scaly skin. A recent study provides dramatic support for the so-called transcription hypothesis of TTD.(1) Specifically, several patients have been shown to carry a mutation in the XPD gene, which encodes a thermolabile form of XPD protein, resulting in loss of hair during febrile episodes.
 ...
PMID:Hot news: temperature-sensitive humans explain hereditary disease. 1149 13