polyadenylointi

Polyadenylointi is a biological process that occurs in eukaryotic cells during gene expression. It involves the addition of a tail of adenine nucleotides to the messenger RNA (mRNA) molecule. This tail, known as the poly-A tail, is typically between 50 and 250 nucleotides long and is added to the 3' end of the pre-mRNA after transcription.

The process is carried out by an enzyme complex that recognizes a specific sequence, AAUAAA, in the pre-mRNA. This recognition site signals the cleavage of the pre-mRNA downstream, and then the poly-A polymerase enzyme adds the adenine nucleotides one by one. Polyadenylointi is a crucial step in the maturation of mRNA and plays several important roles.

One of the primary functions of the poly-A tail is to protect the mRNA from degradation by cellular nucleases, thus increasing its stability and lifespan in the cytoplasm. This allows the mRNA to be translated into protein multiple times. The poly-A tail also plays a role in the export of mRNA from the nucleus to the cytoplasm, where protein synthesis occurs. Furthermore, it is involved in the initiation of translation, helping the ribosome bind to the mRNA and begin the process of protein production. The length of the poly-A tail can also influence the efficiency of translation and the rate of mRNA decay.