Variazioni evolutive e ruolo nella separazione di fase delle ripetizioni amminoacidiche della regione N-terminale di CPEB

Cytoplasmic polyadenylation element binding (CPEB) proteins are a phylogenetically conserved family of regulatory proteins controlling mRNA translation. In mammals, this family is composed of four paralog proteins (CPEB1, CPEB2, CPEB3, and CPEB4), some of which contain multiple homopolymeric amino acid repeats (AARs) and are involved in memory-related long-term synaptic plasticity in neurons. AARs and other low-complexity regions in proteins have been recently identified as drivers of liquid-liquid phase separation (LLPS), a process that can lead to the formation of functional, membrane-less compartments (‘condensates’) in cells. Moreover, AARs in proteins often display complex evolutionary dynamics across protein orthologs, and their length variation contributes to phenotypic evolution by regulating protein function. However, both the evolutionary history of AARs in CPEB proteins and the impact of the evolutionary AAR length variation on CPEB function are poorly understood. To address these issues, through a combination of bioinformatics, molecular and cellular approaches, this research has a twofold scope. First, we systematically define the occurrence and length variation of AARs in CPEB proteins in vertebrates, and in selected invertebrate taxa. Second, we define the functional role of AARs, and of their evolutionary length variation, in the LLPS of CPEB orthologs from model vertebrate (Mus musculus) and invertebrate (Aplysia californica) species. Our evolutionary analyses and biological experiments define novel aspects in the evolutionary history of AAR length variation in CPEBs and highlight its impact on the functional phase transitions of these proteins.