Figure 9.

Nucleolar proteins in the Cajal body. Each pair of panels shows the fluorescent image on the left and the corresponding DIC image on the right. CB, Cajal body; N, nucleolus. (A) Fibrillarin detected with mAb 17C12. The matrices of the Cajal bodies and the nucleoli are equally stained. (B) Nopp140 detected with mAb No114. The matrix of the Cajal body stains more intensely than the dense fibrillar zone of the nucleoli. (C) NO38 (B23) detected with mAb No185. This GV was isolated and spread in the absence of Mg²⁺. Under these conditions the nucleoli lose much of their granular zone, only the matrix of the Cajal bodies remains intact, and the B-snurposomes disappear. Such partially solubilized Cajal bodies retain their NO38, as shown here, as well as their fibrillarin and Nopp140. (D) Nucleolin detected with mAb P71A4, after Mg²⁺-free spreading. Nucleolin is readily detectable in the nucleoli but is absent from Cajal bodies.