REM1 and xeroderma pigmentosum: In this work, by addressing directly the molecular basis for the analogies and differences between several yeast rem mutants (rad3-101, rad3-102 and the newly constructed rad3-107) and by characterizing the effects of XPD-102 in human cells, we show that rem mutants can be used as a model to understand XP-D/CS-associated molecular phenotypes.