Colocalization of codanin-1 with HP1α and Sec23B. (A) Coimmunoprecipitation results. (Left) Whole-cell (WCE) and nuclear (NucE) protein extracts precipitated with the anti-HP1α antibody and blotted with the anti-codanin-1 antibody (COD177). (Right) Protein extracts (WCE, NucE) precipitated with the anti-Sec23B antibody and blotted with the anti-codanin-1 antibody (COD177). Nonspecific bands are immunoglobulins and their complexes. (B) Codanin-1 and Sec23B colocalization in an erythroblast by immunofluorescence. (Ci-ii) Nearest-neighbor distance measurements between codanin-1 and Sec23B foci (and reciprocally) extracted from confocal images from 600 cells. A histogram of simulated nearest-neighbor distance measurements generated in a random model of 10 foci/cell adjusted for volume and contour (cell and nucleus) is plotted in comparison. Each simulated histogram is generated by calculating distances from a random reference focus (Sec23B or codanin-1) to a nearest possible random neighbor focus (codanin-1 or Sec23B) in a virtual cell of similar cyotplasmic and nuclear proportions. The x-axis represents the distance in pixels; and y-axis, the number of distances measured. These graphs suggest that colocalization of codanin-1 and Sec23B is not random. (Ciii) The number of foci/cell impacts simulated histograms. Shown are 2 simulated histograms with either 2 or 10 foci/cell. In the 600 cells analyzed, the average number of foci was approximately 10. (Civ) Representation of Pearson colocalization model (X = 0 center of focus), suggesting colocalization of foci. Background noise accounts for low index values, and only trend is interpretable.