FIG. 2.

to mRNA expression. (A) RNase protection assay showing that to mRNA is down-regulated in clock mutants. WT denotes wild type; rp49 is an internal control. The gel is overexposed to show the low-level signal in per⁰¹, tim⁰¹, and double-mutant flies. (B and C) Northern blots showing the to mRNA cycling profiles in LD (B) and constant dark (C) conditions. To obtain comparable signals, the rp49 probe was about half the length of and 1/40 lower in specific activity than the to probe. Open and filled bars represent the time when light was on (ZT0 to ZT12) and off (ZT12 to ZT24), respectively; the hatched bar represents the subjective day (circadian time [CT] 0 to 12). (D) Quantification of to mRNA levels in panels B and C. The to mRNA signals were normalized to the rp49 signals. DD, constant dark.