Cockayne syndrome: defective repair of transcription?

In the past years, it has become increasingly evident that basal metabolic processes within the cell are intimately linked and influenced by one another. One such link that recently has attracted much attention is the close interplay between nucleotide excision DNA repair and transcription. This is illustrated both by the preferential repair of the transcribed strand of active genes (a phenomenon known as transcription-coupled repair, TCR) as well as by the distinct dual involvement of proteins in both processes. The mechanism of TCR in eukaryotes is still largely unknown. It was first discovered in mammals by the pioneering studies of Hanawalt and colleagues, and subsequently identified in yeast and Escherichia coli. In the latter case, one protein, the transcription repair-coupling factor, was found to accomplish this function in vitro, and a plausible model for its activity was proposed. While the E. coli model still functions as a paradigm for TCR in eukaryotes, recent observations prompt us to believe that the situation in eukaryotes is much more complex, involving dual functionality of multiple proteins.