FIG. 9.

Two models for Tpa1p function. (A) Tpa1p influences poly(A) tail length and mRNP assembly on poly(A) tails in the nucleus and may indirectly influence translation termination following export of the aberrant mRNP to the cytoplasm. (B) Tpa1p is a component of mRNP complexes bound to the 3′ UTR of cytoplasmic mRNAs, where it acts directly to couple translation termination and mRNA deadenylation. Tpa1p denoted by the dashed lines on the right (tpa1Δ) side of the figure indicates the absence of this factor.