FIGURE 3.

Xenopus CCR4 and CAF1 homologs are active deadenylases. A, repeated scheme as in Fig. 1A, except a short radiolabeled RNA was injected instead of reporter mRNAs. The radiolabeled RNA was internally labeled with [α-³²P]UTP and contained three MS2-binding sites and a poly(A) tail of 39 adenosines. RNA was extracted after 16 h of incubation to determine the length of the poly(A) tail with each MS2 fusion protein. B, poly(A) status of reporter RNA. Lanes 1 and 3 show the ³²P RNA without a poly(A) before and after injection into oocytes, respectively. Lanes 2 and 4 show the ³²P RNA with a poly(A) tail before and after injection into oocytes, respectively. Lanes 5–10 indicate poly(A) tail length of the ³²P RNA when tethered to the indicated MS2 fusion protein. Tethered CCR4 and CAF1 excised about 10 nucleotides from the RNA body.³