The role of an E-box element: multiple frunctions and interacting partners

Area of Science:

• * Molecular Biology
• * Chronobiology
• * Plant Science

Background:

• * Circadian clocks regulate daily biological rhythms and can be synchronized by environmental cues like temperature.
• * The green alga Chlamydomonas reinhardtii uses 12-hour temperature shifts between 18°C and 28°C for circadian clock entrainment.
• * The circadian RNA-binding protein CHLAMY1, composed of subunits C1 and C3, plays a role in integrating temperature information.

Purpose of the Study:

• * To investigate the roles of CHLAMY1 subunits C1 and C3 in temperature entrainment of the circadian clock in Chlamydomonas reinhardtii.
• * To elucidate the molecular mechanisms underlying temperature-dependent regulation of C1 and C3 expression.
• * To identify cis-acting elements and transcription factors involved in C3 gene regulation.

Main Methods:

• * Analysis of C1 phosphorylation and C3 expression levels at different temperatures (18°C vs. 28°C).
• * Study of temperature entrainment in the long period mutant per1.
• * Promoter analysis to identify cis-acting elements, including E-box elements, regulating c3 transcription.

Main Results:

• * C1 is hyper-phosphorylated at 18°C, while C3 levels are upregulated at this temperature.
• * Temperature-dependent regulation of C1 and C3 is altered in the per1 mutant.
• * An E-box element in the c3 promoter mediates its upregulation at low temperatures and circadian expression, and is also involved in C1 overexpression effects. C3 interacts with this E-box region, suggesting autoregulation.

Conclusions:

• * CHLAMY1 subunits C1 and C3 are key integrators of temperature signals for circadian clock entrainment in Chlamydomonas reinhardtii.
• * The E-box element is crucial for temperature-responsive and circadian regulation of C3 expression.
• * C3 exhibits autoregulation via interaction with its own promoter's E-box element.