Circadian transcription contributes to core period determination in Drosophila.
The Clock-Cycle (CLK-CYC) heterodimer constitutes a key circadian transcription complex in Drosophila. CYC has a DNA-binding domain but lacks an activation domain. Previous experiments also indicate that most of the transcriptional activity of CLK-CYC derives from the glutamine-rich region of its partner CLK. To address the role of transcription in core circadian timekeeping, we have analyzed the effects of a CYC-viral protein 16 (VP16) fusion protein in the Drosophila system. The addition of this potent and well-studied viral transcriptional activator (VP16) to CYC imparts to the CLK-CYC-VP16 complex strongly enhanced transcriptional activity relative to that of CLK-CYC. This increase is manifested in flies expressing CYC-VP16 as well as in S2 cells. These flies also have increased levels of CLK-CYC direct target gene mRNAs as well as a short period, implicating circadian transcription in period determination. A more detailed examination of reporter gene expression in CYC-VP16-expressing flies suggests that the short period is due at least in part to a more rapid transcriptional phase. Importantly, the behavioral effects require a period (per) promoter and are therefore unlikely to be merely a consequence of generally higher PER levels. This indicates that the CLK-CYC-VP16 behavioral effects are a consequence of increased per transcription. All of this also suggests that the timing of transcriptional activation and not the activation itself is the key event responsible for the behavioral effects observed in CYC-VP16-expressing flies. The results taken together indicate that circadian transcription contributes to core circadian function in Drosophila.
Kadener
Sebastian
S
Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America.
Menet
Jerome S
JS
Schoer
Rebecca
R
Rosbash
Michael
M
D056930:ARNTL Transcription Factors; D000818:Animals; D030801:Animals, Genetically Modified; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D056926:CLOCK Proteins; D002460:Cell Line; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism*; D017405:Herpes Simplex Virus Protein Vmw65 / Q000235:genetics; D009043:Motor Activity / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D056950:Period Circadian Proteins; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014921:Wings, Animal / Q000378:metabolism
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D029721:Drosophila Proteins; D017405:Herpes Simplex Virus Protein Vmw65; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014157:Transcription Factors; C120526:Clk protein, Drosophila; C539040:PER protein, Drosophila; C112805:cyc protein, Drosophila