Cross-contamination between cell lines is a longstanding and frequent cause of scientific misrepresentation. Estimates from national testing services indicate that up to 36% of cell lines are of a different origin or species to that claimed. To test a standard method of cell line authentication, 253 human cell lines from banks and research institutes worldwide were analyzed by short tandem repeat profiling. The short tandem repeat profile is a simple numerical code that is reproducible between laboratories, is inexpensive, and can provide an international reference standard for every cell line. If DNA profiling of cell lines is accepted and demanded internationally, scientific misrepresentation because of cross-contamination can be largely eliminated.

We demonstrate that the nuclear topological arrangement of chromosome territories (CTs) has been conserved during primate evolution over a period of about 30 million years. Recent evidence shows that the positioning of chromatin in human lymphocyte nuclei is correlated with gene density. For example, human chromosome 19 territories, which contain mainly gene-dense and early replicating chromatin, are located toward the nuclear center, whereas chromosome 18 territories, which consist mainly of genepoor and later replicating chromatin, is located close to the nuclear border. In this study, we subjected seven different primate species to comparative analysis of the radial distribution pattern of human chromosome 18-and 19-homologous chromatin by three-dimensional fluorescence in situ hybridization. Our data demonstrate that gene-density-correlated radial chromatin arrangements were conserved during higher-primate genome evolution, irrespective of the major karyotypic rearrangements that occurred in different phylogenetic lineages. The evolutionarily conserved positioning of homologous chromosomes or chromosome segments in related species supports evidence for a functionally relevant higher-order chromatin arrangement that is correlated with gene-density.

Negative elongation factor (NELF) is a four subunit transcription elongation factor that has been implicated in numerous diseases ranging from neurological disorders to cancer. Here we show that NELF interacts with the nuclear cap binding complex (CBC), a multifunctional factor that plays important roles in several mRNA processing steps, and the two factors together participate in the 3' end processing of replication-dependent histone mRNAs, most likely through association with the histone stem-loop binding protein (SLBP). Strikingly, absence of NELF and CBC causes aberrant production of polyadenylated histone mRNAs. Moreover, NELF is physically associated with histone gene loci and forms distinct intranuclear foci that we call NELF bodies, which often overlap with Cajal bodies and cleavage bodies. Our results point to a surprising role of NELF in the 3' end processing of histone mRNAs and also suggest that NELF is a new factor that coordinates different mRNA processing steps during transcription.