Possible relationship of poly(A) shortening to mRNA turnover.

Whereas the original size of poly(A) in HeLa cells is about 200 nucleotides, at steady state most of the poly(A) in mRNA contains less than 50 nucleotides. An endonucleolytic attack on poly(A) is suggested as the most likely method to accumulate short pieces of poly(A). Both poly(A) shortening and mRNA turnover appear to be inhibited by emetine, a drug that stops translation. It is possible that a random endonucleolytic attack leads to scission of poly(A) to a size below which the mRNA is unstable.