Block in Nuclear Localization of period Protein by a Second Clock Mutation, timeless

Abstract

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.

A PER/TIM/DBT Interval Timer forDrosophila's Circadian Clock

“…Subsequently it was shown that the PER and TIM proteins physically interact in vitro, in yeast and Drosophila cells (Gekakis et al 1995;Saez and Young 1996). Interdependent functions of per and tim were also indicated by the finding that PER and TIM coexpression was required for the nuclear accumulation of either protein, and that PER stability was dependent on TIM (Vosshall et al 1994;Price et al 1995;Hunter-Ensor et al 1996;Myers et al 1996). Thus, with the discovery of tim and the regulated nuclear accumulation of PER and TIM (see also Curtin et al 1995), a model was proposed that incorporated the concept of a specific temporal delay to explain how negative feedback could generate oscillations in gene expression.…”

“…A basis for oscillating feedback, and two new classes of molecular cycling (affecting protein stability and subcellular localization), emerged with the discovery of a second-chromosome clock gene called timeless (tim) Vosshall et al 1994). The tim null mutation (tim 0 ) eliminated per RNA and protein oscillations in addition to causing arrhythmic eclosion and locomotor activity .…”

Conservation of gene function in behaviour

“…Three mutations called long (per l ), short (per s ) and arrhythmic (per 0 ) alter eclosion rhythms and circadian patterns of locomotor activity. A second clock gene called timeless (tim) affects circadian rhythmicity and per expression [32][33][34]. Genes per and tim are transcriptionally regulated in a cyclic manner.…”

Modelling of circadian rhythms in Drosophila incorporating the interlocked PER/TIM and VRI/PDP1 feedback loops

“…Therefore, change in degradation rate of PER has also been used in some models (Scheper, Klinkenberg et al 1999;Lema, Golombek et al 2000;Smolen, Hardin et al 2004). Indeed, experimental findings have shown that tim 01 mutants inducing an absence of TIM lead to a substantial lowering of PER abundance (Vosshall, Price et al 1994;Price, Dembinska et al 1995), an effect that happens to be similar to the result of exposing flies to constant light (Zerr, Hall et al 1990;Price, Dembinska et al 1995). Because we did not include the detailed translocation mechanisms of PER and TIM into the nucleus, as well as associated Sgg-dependent TIM phosphorylation and CK2-dependent PER phosphorylation processes in the model (Shafer, Rosbash et al 2002), we simulated the effect of light by increasing the degradation rates of both TIM and PER.…”