 Further studies by the labs of Young, Sehgal, Charles Weitz, and Michael Rosbash indicated that "timeless" protein (TIM) and "period" protein (PER) form a heterodimer that exhibits circadian rhythms in wild type "Drosophila".Researchers in Rosbash's lab also showed that "tim" mRNA levels and TIM protein levels have circadian rhythms that are similar to those of the "period" ("per") mRNA and its product.Experiments done jointly by the Weitz, Young, and Sehgal labs using yeast 2-hybrid proved that TIM directly binds with PER.