A protein results from the translation of a messenger RNA, itself derived from the transcription of a gene. This sequence of gene -> mRNA -> protein has long been presented in biology textbooks as a rather simple progression. And yet, the sequencing of complete genomes makes it possible to say today that the total number of genes does not reflect the plurality of all proteins acting in an organism. The number of proteins is thus at least four times higher than the number of parent genes. Thus, one gene can give rise to several messenger RNAs, known as alternative splicing. Recently, scientists have also become aware that this alternative splicing produces not only messenger RNAs, but also non-coding RNAs (which do not produce proteins) whose functions are poorly understood.
A team from the BIG recently identified several non-coding RNAs that have a circular shape, in the model plant Arabidopsis thaliana. "These non-coding RNAs present themselves in the form of long-lived circular RNA molecules", explains Chloé Zubieta, a researcher at the BIG. "We stimulated the SEPALLATA3 gene, essential for flowering and the development of floral organs, to produce more of a kind of circular RNA, in order to discover its function. It turns out that it is capable of modifying the levels of messenger RNA from the parental gene. Also, the overexpression of this circular RNA gave rise to a floral phenotype that increased the number of petals and decreased the number of stamens in the flower Arabidopsis thaliana."
For the first time, a scientific work shows that circular RNAs can play an essential role in the development of an organism, and suggests that they are regulators of new and powerful genes that previously went unnoticed. These RNAs are not only important in plants, but are key regulators in mammals, as well as in diseases such as cancer. This work opens up new avenues of investigation in gene regulation and alternative splicing, with applications ranging from basic research to targeted therapies.