An arachidonic acid-specific lipoxygenase from the gorgonian coralPseudoplexaura porosa

Summary A novel lipoxygenase was partially purified from the gorgonian coralPseudoplexaura porosa and was found to be specific for arachidonic acid. This soluble enzyme catalyzed the formation of 15-hydroperoxy-eicosatetraenoic acid (15-HPETE) from arachidonic acid.This investigation was supported by PHS grant No. CA32395 awarded by the National Cancer Institute and by PHS Research Carreer Development Award No. ES00120 to MDC awarded by the National Institute of Environmental Health Sciences, DHHS. The authors acknowledge Ms M. A. Russell and Dr D. G. Anderson of the University of Miami for assistance in the collection of gorgonian corals. Preliminary work was conducted at the University of Miami School of Marine and Atmospheric Science. This is journal series No. 3638 from the Florida Agricultural Experiment Station.     

The Collaborative Cross, a community resource for the genetic analysis of complex traits

The goal of the Complex Trait Consortium is to promote the development of resources that can be used to understand, treat and ultimately prevent pervasive human diseases. Existing and proposed mouse resources that are optimized to study the actions of isolated genetic loci on a fixed background are less effective for studying intact polygenic networks and interactions among genes, environments, pathogens and other factors. The Collaborative Cross will provide a common reference panel specifically designed for the integrative analysis of complex systems and will change the way we approach human health and disease.     

Role of transposable elements in heterochromatin and epigenetic control

Heterochromatin has been defined as deeply staining chromosomal material that remains condensed in interphase, whereas euchromatin undergoes de-condensation. Heterochromatin is found near centromeres and telomeres, but interstitial sites of heterochromatin (knobs) are common in plant genomes and were first described in maize. These regions are repetitive and late-replicating. In Drosophila, heterochromatin influences gene expression, a heterochromatin phenomenon called position effect variegation. Similarities between position effect variegation in Drosophila and gene silencing in maize mediated by "controlling elements" (that is, transposable elements) led in part to the proposal that heterochromatin is composed of transposable elements, and that such elements scattered throughout the genome might regulate development. Using microarray analysis, we show that heterochromatin in Arabidopsis is determined by transposable elements and related tandem repeats, under the control of the chromatin remodelling ATPase DDM1 (Decrease in DNA Methylation 1). Small interfering RNAs (siRNAs) correspond to these sequences, suggesting a role in guiding DDM1. We also show that transposable elements can regulate genes epigenetically, but only when inserted within or very close to them. This probably accounts for the regulation by DDM1 and the DNA methyltransferase MET1 of the euchromatic, imprinted gene FWA, as its promoter is provided by transposable-element-derived tandem repeats that are associated with siRNAs.