Fig. 3. UAP56 was most concentrated at the periphery of interchromatin granule clusters. Anti-UAP56 antibody and 5 nM gold-bead-conjugated secondary antibodies were used for the pre-embedment staining of CaSki cells with an EDTA regressive counter stain. Although UAP56 was present throughout the cluster, the largest concentration of gold beads was at the periphery of the cluster, where interchromatin granules meet perichromatin fibrils. This is the region of the nucleus in which the majority of transcripts are spliced and from which they are released to the cytoplasm. (A) A low-magnification view of a cell with an EDTA-treatment time of 30 minutes. (B) A high-magnification view of the interchromatin granule cluster indicated in A. The 5-nm gold beads have been highlighted with a yellow overlay to make them easier to distinguish.