mRNA acts as a carrier of genetic information and is exported from the nucleus into the cytoplasm, serving as a template for protein production by the ribosomal machinery. The efficiency of protein production is greatly dependent on mRNA stability and the turnover of mRNA in the cytoplasm is constantly regulated by numerous protein complexes to maintain proper protein levels. Eventually, after translation, all mRNA undergoes degradation, however, aberrant mRNA degradation may lead to disease. Two general mechanisms protect mRNA against premature degradation which are incorporation of a 7-methyl guanosine (m 7 G) as a 5'-cap and by connection of a poly-adenine stretch (poly(A) tail) to the 3'-terminus. The 5'-cap-binding complex provides resistance against the 5' to 3' exonucleases , whereas poly(A)-binding protein (PABP) coats the poly(A) tail to protect it from exonuclease cleavage from the 3' end. Poly(A) tails also play an important role in mRNA export to the cytoplasm and help to form a closed loop via interaction of PABPs with cap binding proteins to promote translation. The average length of poly(A) tails in mammals is ~200 nt and the length of it is directly correlated to the translational efficiency of the mRNA transcript.