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. Author manuscript; available in PMC: 2013 Jun 1.
Published in final edited form as: Biochim Biophys Acta. 2012 Mar 28;1819(6):546–554. doi: 10.1016/j.bbagrm.2012.03.006

Fig. 3. Models for Nab2 control of poly(A) tail length.

Fig. 3

In a polyadenylation limiting model, Nab2 interacts with cleavage and polyadenylation factors (cleavage factor I (CFI); cleavage and polyadenylation factor (CPF)) or potentially alters the poly(A) RNA conformation to restrict poly(A) polymerase activity and limit poly(A) tail length. In the poly(A) tail trimming model, Nab2 recruits and modulates/stimulates a ribonuclease to trim the poly(A) tail to the correct length. Although, Nab2 is depicted with the cleavage and polyadenylation machinery during recruitment of a ribonuclease, Nab2 could also recruit a ribonuclease after polyadenylation at a later stage in mRNA biogenesis. These models are not necessarily mutually exclusive.