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Abstract
An endogenous clock regulates the temporal expression of genes/mRNAs that are involved in the circadian output pathway. In the bioluminescent dinoflagellate Gonyaulax polyedra circadian expression of the luciferin‐binding protein (LBP) is controlled at the translational level. Thereby, a clock‐controlled RNA‐binding protein, called circadian controlled translational regulator (CCTR), interacts specifically with an UG‐repeat, which is situated in the lbp 3′ UTR. Its binding activity correlates negatively with the amount of LBP during a circadian cycle. In the green alga Chlamydomonas reinhardtii, a clock‐controlled RNA‐binding protein (CHLAMY 1) was identified, which represents an analog of the CCTR from the phylogenetically diverse alga G. polyedra. CHLAMY 1 binds specifically to the 3′ UTRs of several mRNAs and recognizes them all via a common cis‐acting element, composed of at least seven UG‐repeats. The binding strength of CHLAMY 1 is strongest to mRNAs, whose products are key components of nitrogen metabolism resulting in arginine biosynthesis as well as of CO2 metabolism. Since temporal activities of processes involved in nitrogen metabolism have an opposite phase than CHLAMY 1 binding activity, the protein might repress the translation of the cognate mRNAs.
| Abbreviations | ||
| Arg | = | arginine |
| Arg‐suc | = | arginino‐succinate |
| Arg7 | = | gene encoding ASL |
| ASL | = | arginio‐succinate lyase |
| CCTR | = | circadian controlled translational regulator |
| Gln | = | glutamine |
| GS2 | = | chloroplastic glutamine synthetase |
| LBP | = | luciferin‐binding protein |
| LCF | = | luciferase |
| Lip 36‐G1 | = | CO2 shuffling protein in outer chloroplast membrane |
| L‐POR | = | light‐dependent NADPH‐protochlorophyllide‐oxido reductase |
| Lpcr‐1 | = | gene encoding the light‐dependent POR |
| Nii | = | nitrite reductase |
| NRT2;3 | = | nitrite/nitrate transporter |
| RbcS1 | = | small subunit of RUBISCO |
| UTR | = | untranslated region |
| uORF | = | upstream open reading frame |
| Yptc4 | = | G‐protein |
| Abbreviations | ||
| Arg | = | arginine |
| Arg‐suc | = | arginino‐succinate |
| Arg7 | = | gene encoding ASL |
| ASL | = | arginio‐succinate lyase |
| CCTR | = | circadian controlled translational regulator |
| Gln | = | glutamine |
| GS2 | = | chloroplastic glutamine synthetase |
| LBP | = | luciferin‐binding protein |
| LCF | = | luciferase |
| Lip 36‐G1 | = | CO2 shuffling protein in outer chloroplast membrane |
| L‐POR | = | light‐dependent NADPH‐protochlorophyllide‐oxido reductase |
| Lpcr‐1 | = | gene encoding the light‐dependent POR |
| Nii | = | nitrite reductase |
| NRT2;3 | = | nitrite/nitrate transporter |
| RbcS1 | = | small subunit of RUBISCO |
| UTR | = | untranslated region |
| uORF | = | upstream open reading frame |
| Yptc4 | = | G‐protein |