Polyadenylation

As polyadenylation is known to attach adenine nucleotides, called poly ( A) tail at the 3 'end of eukaryotic (including viral ) pre-mRNA by the enzyme poly (A) polymerase. The polyadenylation is exactly like the splicing and capping, a post-transcriptional modification of eukaryotic pre-mRNA.

The poly ( A) tail is not encoded by the DNA, but by the enzyme poly (A) polymerase, while the processing of the pre-mRNA ( hnRNA ) in the cell nucleus at the 3 ' end of the pre-mRNA Linked. The processed mRNA is referred to as poly ( A) mRNA. The length of the poly ( A) tail varies from organism to organism (baker about 80 nucleotides, about 250 nucleotides in mammals ). The poly ( A) tail is from the poly (A) binding protein ( PABP ) occupied and is necessary for the initiation of translation.

The polyadenylation many proteins are involved, such as the multimeric protein CPSF ( cleavage and polyadenylation specificity factor), which recognizes the polyadenylation signal (5 ' ... AAUAAA ... 3'). The poly ( A) binding protein ( PABPN1 ) binds during the synthesis of the growing poly ( A) tail. The poly ( A) tail is shortened still further with advancing age of the mRNA molecule and regulates its half-life.

The functions of the poly ( A) tail are not fully understood, but certainly are an increase in mRNA stability by protecting against degradation and an increase in translatability. A 7- methylguanosine nucleotide ( CAP structure ) binds to the 5 'end and also serves to protect the degradation.

On the degradation of the mRNA is a bacterial protein complex, the Degradosom involved.