Diversity in Nuclear Pore Complexes Figure 7. Nuclear distribution of NPC populations varies with cell type. Double immunofluorescence analyses of NUP62 (green) and NUP214 (red) are shown for large fields of subconfluent TOV112D ovarian carcinoma, COS7, S12 neuroblastoma, and HEK293 cells. Blue, DAPI stain; yellow, overlap between green and red. Bar represent 10 um. doi:10.1371/journal.pone.0036137.g007 same NPC, while studies of epitope-tagged NUP62 and NUP214 supported the conclusion that differences the immunolabeling patterns observed using native antibodies resulted from the presence or absence of nucleoporins and not from post-translation modifications affecting antibody binding. Immunoblot analyses suggest that posttranslational modifications may attenuate binding of the NUP214 antibody in Western blot applications, but this putative modification does not appear to affect the pattern of NPC immunolabeling observed with this antibody in immunofluores- cence applications. Sorting of NUP62 and NUP214 to different NPC populations does not conflict with other data showing that NUP62 and NUP214 can physically associate [36]. Physical association of NUP62 and NUP214 has been observed in cell lysates and using recombinant proteins in vitro, and such studies do not directly address the distribution of the NUP62/NUP214 association in vivo. Clearly, complexes of NUP62 and NUP214 may form in those NPCs which contain both nucleoporins. In addition, recombinant NUP62 bound a form of NUP214 from cell lysates that migrated slower during SDS-PAGE than the form(s) that bound other nucleoporins, such as NUP153 [36]. Immuno- blot analyses presented here also suggest the presence of slower and faster migrating forms of NUP214, and future studies may reveal a correlation between the expression or accumulation of NUP214 forms and the distribution of NUP62 and NUP214 among NPC populations in different cell types. Several studies have shown that distribution of NPCs reflects the transcriptional disposition of the underlying chromatin [54]. In general, DNA in the vicinity of the nuclear envelope in metazoans appears heterochromatic and to contain silent genes [55]. Studies in C. elegans have indicated that during cellular differentiation, induction of transcription is accompanied by gene migration from the periphery to central regions of the nucleus [56]. Consistent with these findings are studies in Drosophila salivary and embryonic cells showing that a large set of genes involved in cell cycle regulation and development make contact with FG- containing nucleoporins in the nucleoplasm at sites distal to the NPC. As determined by histone H3 methylation, histone H4 acetylation, and other criteria, these genes on average are PLoS ONE | www.plosone.org 9 April 2012 | Volume 7 | Issue 4 | e36137