In the past years, it has become increasingly evident that basal metab
olic 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 tra
nscription, This is illustrated both by the preferential repair of the
transcribed strand of active genes (a phenomenon known as transcripti
on-coupled repair, TCR) as well as by the distinct dual involvement of
proteins in both processes, The mechanism of TCR in eukaryotes is sti
ll largely unknown, It was first discovered in mammals by the pioneeri
ng studies of Hanawalt and colleagues, and subsequently identified in
yeast and Escherichia coli, In the latter case, one protein, the trans
cription 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 eukaryo
tes is much more complex, involving dual functionality of multiple pro
teins.