Figure 1.

Schematic overview of six main members of the CRY/PL family based on their function in major model organisms and references given in the introduction. (A,B) The photosensitive photolyases repair UV-induced pyrimidine-pyrimidone dimer mutations in DNA using blue light. Depending on the type of mutation they repair, they are called 6-4 photolyases (pyrimidine-pyrimidone-6-4 photoproduct) or CPD photolyases (cyclobutane-pyrimidine dimer). Plant PCRYs (C) are photosensitive and directly or indirectly affect the transcription of several genes whose functions are also linked to the circadian clock. The Drosophila light-sensitive cryptochrome (DCRY) is activated by blue light and destabilizes TIMELESS, resulting in a resetting of the circadian clock (D). The mammalian light insensitive MCRY, which is also involved in the circadian clock, acts as an indirect transcription factor, and inhibits its own expression (E). DASH-CRYs (F) act as a link between different members of the CRY/PL family. They appear to be involved in both the circadian clock and the repair of mutations in single-stranded DNA.