FIG. 4.

Mpp6 displays in vitro RNA binding activity. ³⁵S-labeled Mpp6 was generated from a TNT reaction and incubated with resins carrying the factors indicated. Following incubation, proteins were recovered from bound and unbound fractions. Equivalent amounts were run along with the corresponding input (lane 1) on a 4 to 12% Bis-Tris gradient acrylamide gel and visualized by autoradiography. Resins used were protein A-Sepharose (protein A), poly(U)-Sepharose [poly(U)], streptavidin agarose alone (Strep), and streptavidin-agarose loaded with either biotinylated A₂₀ [poly(A)], biotinylated A₂₀/U₂₀ [poly(A/U)], biotinylated dT₂₀ [poly(dt)], or an in vitro-transcribed and biotinylated pre-rRNA fragment (D-A2 RNA) or tRNA^imet (tRNAmet).