FIG. 4.

RNA and the interaction between NP and F-actin. (a) Effect of actin on the RNA-binding activity of NP. The amounts of radiolabelled RNA (1 nM) bound by MBP (circles), MBP-NP (squares), and MBP-NP plus 3 μM F-actin (triangles) were determined by a filter assay. (b) Effect of RNA on actin binding by NP. MBP-NP (0.75 μM) was cosedimented in the presence (+) or absence (−) of 3 μM F-actin with the indicated molar ratio of a 34-mer RNA. S, supernatant; P, pellet. (c) Cosedimentation of RNA with actin and NP. Radiolabelled 34-mer (100 nM in 100 μl; open bars) or 54-mer (50 nM; shaded bars) was cosedimented in the presence of 3 μM MBP-NP with or without 3 μM F-actin.