Are RNA granules liquid organelles? Regulation of P granule dynamics by intrinsically-disordered proteins
2017
Geraldine Seydoux
Summary of the science
DNA holds all the information required for our cells to function properly. When a specific gene is needed, that section of DNA is copied into RNA, the 'messenger' for DNA. RNA then acts as a temporary blueprint to make proteins. Some RNA molecules form granules. These are structures found within cells that contain RNA molecules and associated proteins, and are used as a centre for RNA processing, storage and regulation. They have been compared to liquid droplets due to their liquid consistency and dynamics. The Seydoux Lab has been investigating how these granules are secured in the cell. In their experiments, specific proteins, described as 'intrinsically disordered' because they lack a fixed 3D structure, were found to form a gel-like substance after they receive a signal from RNA - this gel secures RNA granules in the cell and makes sure they are functioning properly. P granules are a type of RNA granule found in the sex cells of C.elegans, a common worm that is used in research as a model organism.
About the research
The Seydoux Lab use a combination of genetics, microscopy and biochemistry to investigate RNA and protein dynamics in the cytoplasm. RNA granules are formed of protein/RNA condensates through liquid-liquid phase separation. Liquid-liquid phase separation is the spontaneous separation of a homogeneous liquid mixture into two distinct liquid phases driven by changes in environmental conditions or molecular interactions. Seydoux and colleagues have found that these RNA granules are secured in the cytoplasm in a gel-like coat consisting of intrinsically disordered proteins that form a gel in vitro after being stimulated by RNA. Other eukaryotic cells are thought to possibly have adapted this mechanism to secure liquid condensates within the cytoplasm.
About the illustration