Vosshall, L.B., Price, J.L., Sehgal, A., Saez, L., Young, M.W. (1994). Block in nuclear localization of period protein by a second clock mutation, timeless.  Science 263(5153): 1606--1609.

FBrf0068725

Research paper

In wild-type Drosophila, the period protein (PER) is found in nuclei of the eyes and brain, and PER immunoreactivity oscillates with a circadian rhythm. The studies described here indicate that the nuclear localization of PER is blocked by timeless (tim), a second chromosome mutation that, like per null mutations, abolishes circadian rhythms. PER fusion proteins without a conserved domain (PAS) and some flanking sequences are nuclear in tim mutants. This suggests that a segment of PER inhibits nuclear localization in tim mutants. The tim gene may have a role in establishing rhythms of PER abundance and nuclear localization in wild-type flies.