CSB mutations and mild UV sensitivity: what researchers found

A single protein, functioning at reduced capacity, separates two very different diagnoses.\n\nWhen ultraviolet light damages DNA inside a cell, a repair process called transcription-coupled nucleotide excision repair — TC-NER — moves in to clear the obstruction. According to a study published in the Journal of Investigative Dermatology, this system depends on a cascade of proteins, beginning with one called CSB, which recognises the point where RNA Polymerase II has stalled on a strand of damaged DNA.\n\nWithout CSB, the researchers reported, that repair process cannot start. Two other proteins — CSA and UVSSA — are recruited only after CSB does its work. Loss of any one of the three, the study found, produces complete TC-NER deficiency.\n\n## Two syndromes, one gene\n\nMutations in the gene that produces CSB are most commonly associated with Cockayne syndrome, a condition the study described as marked by neurodegeneration and severe premature aging. The researchers noted that Cockayne syndrome illustrates how consequential TC-NER failure can be: without the repair mechanism, transcription-blocking lesions accumulate and become, in the study's phrasing,