The "timeless" gene is an essential component of the molecular circadian clock in "Drosophila". It acts as part of an autoregulatory feedback loop in conjunction with the period (per) gene product as noted in collaborative studies performed by the labs of Michael W. Young and Amita Sehgal. 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. During the early evening, PER and TIM dimerize and accumulate. Late at night, the dimer travels into the nucleus to inhibit "per" and "tim" transcription. In 1996, the teams of Sehgal, Edery, and Young found that exposure to light leads to the degradation of TIM and subsequently PER.