Novel interaction of two clock-relevant RNA-binding proteins C3 and XRN1 in Chlamydomonas reinhardtii

The RNA-binding protein CHLAMY1 of the green alga Chlamydomonas reinhardtii consists of two subunits, named C1 and C3 that maintain the period and phase of the circadian clock. Here, we investigated if any of its subunits interact with other clock components involved in RNA metabolism. We found that C3, but not C1 strongly interacts with exoribonuclease XRN1 whose knockout results in low amplitude rhythms. XRN1 is subject to degradation by the proteasome pathway. Its level increases in cells grown at lower ambient temperature simulating night, which was also observed for C3. Our data indicate a network of clock-relevant RNA-binding proteins.Structured summary of protein interactionsXRN1 physically interacts with C3 by anti bait coimmunoprecipitation (View interaction)XRN1 physically interacts with C3 by two hybrid (View interaction)C1 physically interacts with C3 by two hybrid (View interaction)

► XRN1 interacts with the C3 subunit of CHLAMY1. ► XRN1 does not significantly interact with the C1 subunit of CHLAMY1. ► XRN1 is degraded by the proteasome pathway. ► XRN1 is increased in cells grown at lower ambient temperature simulating the night.