Fig. 4.

The non-poly(A) binding portion of PABP1 is sufficient to block TTP-induced deadenylation. A: poly(A) and non-poly(A) binding portions were cloned and expressed in Escherichia coli separately, shown as a wet-gel scan of Coomassie-stained GST-PABP1-RRM1+2 and GST-PABP1-RRM3+4-COOH terminus PABP truncations. B: truncation proteins enhance TTP-binding to a radioactive TNF probe, although less than the full-length PABP1 protein. C: TTP-directed deadenylation is inhibited by the truncation mutants RRM3+4C, which contains the ARE-binding region, but not the poly(A) binding region. These experiments have been performed >3 times with equivalent results.