[Intramolecular double-stranded helices of polyadenylic acid and their possible biological significance]

Under protonation of the single-stranded polyadenylic acid so called "frozen" form arises simultaneously with formation of two double-stranded forms. It has been shown that a portion of the polyadenylic acid "frozen" form increases with the size of poly(A) and ionic strength of solution, i. e. with an increase of polymer chain flexibility. These findings may be considered as evidences in favor of our earlier supposition on poly(A) ability to fold with formation of intramolecular double-stranded helices. Ten years ago we also proposed a hypothesis that such double-stranded helices can be formed in poly(A) tracts of cellular RNAs and they can participate in several biological processes. An analysis of literature data published later evidences for the hypothesis adequacy and shows that it still remains urgent.