The ends of mRNA molecules are specifically modified in order to enhance their stability and ability to serve as a template for proteins synthesis at ribosomes: at the beginning, they contain so-called cap structure, while at the end, there is a poly(A) tail. The poly(A) tail is a homopolymeric tract of adenosine nucleotides added by specific enzymes. Nearly all mRNAs in the cell are polyadenylated in the nucleus right after being transcribed from DNA and before the transport to the cytoplasm. However, there is growing evidence that the process of polyadenylation can also take place in the cytoplasm and is therefore called cytoplasmic polyadenylation. In neurons, cytoplasmic polyadenylation of synaptic mRNAs plays a significant role in the regulation of protein synthesis. However, until now it was studied only for a few mRNAs, and the global impact of this phenomenon and the specific enzymes carrying out the reactions are unknown.