Trf4p Is the Catalytic Subunit of a New Poly(A) Polymerase

<div><p>(A) The Trf4 complex has poly(A) polymerase activity. The 5′-end-labeled oligo(A)₁₅ was incubated 30 min with 5, 10, or 20 ng of affinity-purified fractions of the wild-type TAP-tagged Trf4p (Trf4-TAP) or mutant Trf4p with the aspartic acid residues 236 and 238 changed to alanines (DADA-TAP). Protein was omitted in lane 1. Recombinant yeast poly(A) polymerase (Pap1), 1, 2, and 4 ng, was used as a positive control. The migration position of oligo(A)₁₅ is indicated by an arrow.</p> <p>(B) The Trf4p activity is specific for the addition of adenosine monophosphate. Polyadenylation assays with 20 ng of Trf4-TAP in the presence of different ribonucleoside triphosphates. Recombinant yeast Pap1p, 5 ng, was used as a control. All samples were separated on 15% denaturing gels.</p>