Cellularclocks allow organisms to anticipate the environmental cycles of day and nightby synchronizing their internal, circadian rhythms with the rising and settingof the sun. In cyanobacteria the clockconsists of solely three proteins - KaiA, KaiB and KaiC - orchestrating geneexpression. Complex formation between Kai proteins and, therefore, theirstoichiometry is essential in maintaining robust circadian oscillations. Thus,it is puzzling that several cyanobacteria, e.g.
Synechocystis, contain multiple
kai-genecopies. Our global transcriptomicanalyses of light-dark synchronised
Synechocystis cultures indicate arather light-driven than a circadian regulated pattern in global geneexpression. We detected several small RNAs encoded at the
kai gene locibut antisense to
kai genes whichmight be involved or even interfere with circadian regulation. Besides severalother studies, we have already shown how small RNAs can influence the temporalregulation of gene expression. Thus, regulation by antisense RNA might be afundamental mechanism for the daily coordination in cyanobacteria.Althoughthe expression of many gene transcripts fluctuates over day and night, thesewere less pronounced at the protein level. Therefore, abundance and constituencywere probed of protein complexes present in cyanobacteria using size exclusionchromatography-based proteomics. Following complexes such as the RNApolymerase, the ribosome and complexes involved in photosynthesis, we observethat these complexes change not only in abundance but also in constituency,with associated proteins being either present or absent. We conclude that thedynamic assembly of protein complexes is also a key-player in the processesgoverning the daily rhythm. Why I decided and how Imanage being a female researcher and mother of two children while researchingon regulatory RNAs and circadian clock for about 15 years now, I am going torecapitulate.
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