Many environmental factors, such as ultraviolet (UV) light from the sun, can mutate DNA. Normally, cells maintain repair mechanisms to counter mutations. The protein XPD belongs to a complex of proteins that mediates a type of DNA repair (called nucleotide excision repair) that corrects defects induced by UV light. Mutant XPD is the cause of three syndromes involving sensitivity to UV light, one of which is trichothiodystrophy (TTD).
The protein XPD is also required for the transcription of DNA into RNA (transcription is the first step in the production of proteins from genes). Mutations that give rise to TTD disrupt both DNA repair and transcription. Now, Jan Hoeijmakers and colleagues (of Erasmus University, Netherlands) report that some of these mutations inactivate XPD at high temperature, such as that produced by fever (Nature Genetics, Vol. 27, No. 3, 02 Mar 2001). And so people who carry these mutations suddenly lose their hair when fighting off severe infections. The researchers show that this is due to a reduction of XPD-dependent transcription--which affects some genes more than others. They propose that the genes encoding some constituents of hair fibers--called 'keratin-crosslinkers'--fall into this category because they are heavily transcribed in normal mature hair cells. They reckon that at high temperature, the patients' hair fibers are depleted of keratin crosslinkers and thus become brittle enough to break.
Dr. Jan H.J. Hoeijmakers
Telephone: (31) 10 408 7199
Fax: (31) 10 408 9468
Dr. Priscilla K. Cooper
Lawrence Berkeley National Laboratory
Berkeley, California, USA
Telephone: +1 (510) 486-7346
Fax: +1 (510) 486-6816
(C)Nature Genetics press release.
Message posted by: Trevor M. D'Souza