The mechanism by which heterochromatin mediates the epigenetic gene-silencing events that cause position effect variation (PEV) is not understood. Two articles in the November Molecular Cell from Janssen and colleagues explore the role of repetitive heterochromatin sequences in PEV (Mol Cell 2000, 6:999-1011 and 1013-1024). In the first article, Janssen et al. describe the development of satellite-specific DNA minor groove binding drugs containing pyrrole and imidazole amino acids (polyamides).

Chromatin insulators protect genomic domains from chromosomal position effects and from enhancer activation, but the mechanisms by which the insulators function are largely unknown. In the November Molecular Cell Gerasimova et al. provide insights by analyzing the behavior of the gypsy insulator in diploid interphasic cells from Drosophila imaginal disks (Mol Cell 2000, 6:1025-1035). They employed three-dimensional constructions of immunofluorescence microscopy images to investigate the nuclear

Nuclear localization signals (NLSs) are motifs that mediate the transport of proteins to the nucleus, but finding an NLS within your protein of interest can be tricky. In the 15 November EMBO Reports (EMBO Reports 2000, 1:411-415), Cokol et al. describe an 'expert database' of NLSs, created by collecting 91 experimentally determined NLSs and extending the dataset by 'in silico mutagenesis'. They initially increased the database by adding homologous proteins, and then analyzed sets of proteins wi

In the 15 November EMBO Reports Klinakis et al. describe a method for insertional mutagenesis and gene tagging that uses transposon-mediated mutagenesis (TRAMM) (EMBO Reports 2000, 1:416-421). They used two plasmid vectors, one encoding the Minos transposase enzyme from Drosophila hydrei and the other carrying a drug-resistance gene flanked by Minos inverted repeats. The naked DNA plasmids were transfected into human HeLa cells and about 4% of cells gave drug-resistant clones with multiple inser

The nuclear-encoded RNA polymerase RpoT;2 from Arabidopsis thaliana differs from the polymerases that transcribe the plant's nuclear genes and resembles RNA polymerases from bacteriophages. In the 15 November EMBO Reports, Hedtke et al. describe the use of GFP (green fluorescent protein) fusion proteins to examine the subcellular localization of RpoT;2 (EMBO Reports 2000, 1:435-440). The RpoT;2 transit peptide targeted GFP fusion proteins to both mitochondrial and chloroplast compartments in tob

Insulators define independent genomic regions that are protected from the influence of distant regulatory sequences. In the 1 November EMBO Journal, Parnell and Geyer describe a novel application of the FLP recombinase to investigate the properties of two Drosophila insulators, called gypsy and scs (EMBO J 2000, 19:5864-5874). Neither insulator affected FLP recombination and protein-protein interactions at adjacent recombination sites, suggesting that gypsy and scs do not act by general inhibiti

The elimination of specific DNA elements is a common feature in the formation of a transcriptionally active macronucleus during the sexual reproduction of ciliated protozoa. The micronuclear DNA of Paramecium tetraurelia contains some 50,000 internal eliminated sequences (IES), each of which is flanked by TA dinucleotide repeats and inverted sequences. In the November Molecular and Cellular Biology Ku et al. describe an in vivo method to analyse IES excision (Mol Cell Biol 2000, 20:8390-8396). T

Nuclear BTB/POZ proteins are often concentrated into discrete nuclear subdomains, but the role of these nuclear compartments is unclear. The BCL6 proto-oncogene, frequently altered in non-Hodgkin lymphoma, encodes a POZ/zinc finger protein that shows a characteristic localization in nuclear aggregates. In the November Molecular and Cellular Biology Albagli et al. used a tetracycline-regulated, epitope-tagged BCL6 allele to explore the significance of BCL6 aggregates (Mol Cell Biol 2000, 20:8560-

Transgenic animals carrying a prokaryotic vector are useful tools for mutation studies and the detection of spontaneous or induced mutations in different tissues. Advances in fish transgenesis make it possible to develop fish that can be used both to assess the health hazards of mutagens in aquatic environments and for comparative mutagenesis analysis. In a paper published online ahead of print in Proceedings of the National Academy of Sciences, Winn et al. report the use of a bacteriophage lamb

The timing of flowering in plants is affected by a wide range of hormonal, environmental and genetic factors. The semidominant fwa mutants are delayed in the transition to flowering. In the October Molecular Cell, Soppe et al. use positional cloning to isolate the Arabidopsis FWA gene, which encodes a homeodomain-containing protein (Molecular Cell 2000, 6:791-802). The late-flowering phenotype of the fwa mutants is caused by gain-of-function epi-alleles. Soppe et al. could find no differences

DNA-binding transcription factors can target the SWI/SNF chromatin remodelling complex to specific nucleosome sites.

RNA interference (RNAi) is an elegant technique in which double-stranded RNA (dsRNA) can direct the degradation of homologous RNA species leading to post-transcriptional gene silencing. In the October 2 EMBO Journal Mette et al. extend dsRNA applications by showing that dsRNA corresponding to sequences from the nopaline synthase promoter (NOSpro) could disrupt transcriptional activation (EMBO Journal 2000, 19:5194-5201). The dsRNA trans-silencing was accompanied by induced methylation of the tar