摘要：

In order to determine whether the functional capacity of polyadenylated messenger RNA is altered when the poly(A) segment is shortened as a consequence of mRNA aging, we compared the abilities of differentially labeled new and old mRNAs to engage ribosomes. Experiments were performed using both exponentially growing mouse L cells and L cells in which the polyribosomes were temporarily disassembled as a result of a temperature shock. Our results indicate that new and old messages engage ribosomes with roughly equivalent efficiencies, suggesting, therefore, that length of poly(A) is not a determining factor for mRNA translation. We then examined the question of whether an mRNA that was originally polyadenylated could function if the Poly(A) segment were removed. This was accomplished by submitting polyadenylated mRNA to a limited digestion with a 3′-OH specific exoribonuclease, reisolating the residual polyadenylated and deadenylated mRNA, and measuring their template activities using a cell-free protein synthesizing system prepared from wheat embryos. Such experiments also failed to reveal any effect of the poly(A) on the translational capacity of the mRNA.

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