The ARE-associated factor AUF1 binds poly(A) in vitro in competition with PABP

Francis Sagliocco , Benoît Laloo , Bertrand Cosson , Laurence Laborde , Michel Castroviejo , Jean Rosenbaum , Jean Ripoche , Christophe Grosset (1)

1 E362 INSERM

The AU-rich element (ARE) is a post-transcriptional element controlling both mRNA turnover and translation initiation by primarily inducing poly(A) tail shortening. The mechanisms by which the ARE-associated proteins induce deadenylation are still obscure. One possibility amongst others would be that an ARE/ARE-binding protein complex intervenes on the PABP/poly(A) tail association and facilitates poly(A) tail accessibility to deadenylases. Here we show by several experimental approaches that AUF1/hnRNP D, an mRNA-destabilizing ARE-binding protein, can bind poly(A) sequence in vitro. First, endogenous AUF1 proteins from HeLa cells specifically bound poly(A), independently of PABP. Second, using polyadenylated RNA probes, we showed that (i) the four recombinant AUF1 isoforms bind poly(A) as efficiently as PABP, (ii) the AUF1 binding to poly(A) does not change when the polyadenylated probe contains the GM-CSF ARE, suggesting that in vitro, the AUF1/poly(A) association was independent of the ARE sequence per se. In vitro, the binding of AUF1 isoforms to poly(A) displayed oligomeric and cooperative properties and AUF1 efficiently displaced PABP from the poly(A). Finally, the AUF1 molar concentration in HeLa cytoplasm was only twice lower than that of PABP, whereas in the nucleus, its molar concentration was similar to that of PABP. These in vitro results suggest that in vivo, AUF1 could compete with PABP for the binding to poly(A). Altogether our data may suggest a role for AUF1 in controlling PABP/poly(A) tail association.

Mots clés: Life Sciences

Francis Sagliocco, Benoît Laloo, Bertrand Cosson, Laurence Laborde, Michel Castroviejo, et al.. The ARE-associated factor AUF1 binds poly(A) in vitro in competition with PABP. Biochemical Journal, 2006, 400 (2), pp.337-347. ⟨10.1042/BJ20060328⟩. ⟨hal-00478545⟩