A solid scaffolding for cells

To perform the task for which they have been synthesized, proteins must first assemble to form effective cellular "machines." But how do they recognize their partners at the right time? Researchers at the University of Geneva (UNIGE) have deciphered the fundamental role of the Not1 protein, conserved in all eukaryotic organisms: by regulating the activity of ribosomes, the "protein factories" of cells, Not1 allows proteins that must work together to be synthesized in the same place and at the same time. The identification of this previously unknown mechanism helps to better understand one of the most fundamental elements of cellular machinery, which, if it malfunctions, causes many diseases. Results are published in Nature Structural & Molecular Biology.
In human cells, like in all eukaryotic organisms, genetic material is found in the nucleus in the form of DNA. To perform the genetic programme encoded by DNA, it must first be transcribed into RNA, which in turn is translated into proteins. This job is done by the ribosomes, small machines that produce proteins by decoding RNA.

Once synthesized, the proteins arrive in the cytoplasm, between the nucleus and the membrane, where most of the cell activity takes place. However, to function properly, proteins must assemble to form cellular machines and perform the tasks for which they were produced. "The cytoplasm is cluttered with quantities of proteins, RNAs, and organelles," says Martine Collart, a professor at the UNIGE Faculty of Medicine, who led this work. "Let's imagine a giant concert with a group of musicians. The room, crowded with spectators, has dozens of doors. How will the musicians, in the middle of this huge crowd, all meet in time to perform? This is what happens at every moment in the cytoplasm: proteins belonging to the same complex must find each other and assemble to function properly."