Accessory Sequences Research Articles

Characteristics and Significance of the Polyadenylate Sequence in Mammalian Messenger RNA

This chapter describes that the poly (A) segment in mRNA provides a dramatic example of an accessory polynucleotide sequence that is clearly not involved in the primary function of the RNA chain. All RNA types seem to possess extra sequences of this kind. The precursor molecules to ribosomal RNA, messenger RNA and transfer RNA also contain large polynucleotide segments that are eliminated during the maturation process. The unique thing about poly (A) segment is that it represents a homopolymeric sequence and that its size is subject to variation. This segment provides a highly specialized structure that identifies a class of RNA in the cell. It does not allow for any diversity to permit discrimination between different species of mRNA. This type of sequence is useful to the biochemist, as it permits the detection and isolation of a unique RNA class. It is presumably also useful to the cell, although its precise function remains elusive. Further studies will reveal a variety of regulatory functions for the accessory polynucleotide sequences in the cell.