Electronmicroscopic studies of active genes

Structural aspects of ribosomal and non-ribosomal RNA transcription are compared and contrasted in a representative prokaryote (Escherichia coli) and in several diverse eukaryotes (developing amphibian oocytes, Drosophila melanogaster embryos, HeLa cells, and yeast). The conformations of these active loci are described in relation to genetic and biochemical studies of the activity of the two major classes of genes.BARBARA A. HAMKALO, OSCAR L. MILLER, JR., AIMMEE H. BAKKEN, Departments of Molecular Biology and Biochemistry and Developmental and Cell Biology, University of California, Irvine, California ; Department of Biology, University of Virginia, Charlottesville, Virginia ; Department of Zoology, University of Washington, Seattle, Washington

A unified phylogeny-based nomenclature for histone variants

Histone variants are non-allelic protein isoforms that play key roles in diversifying chromatin structure. The known number of such variants has greatly increased in recent years, but the lack of naming conventions for them has led to a variety of naming styles, multiple synonyms and misleading homographs that obscure variant relationships and complicate database searches. We propose here a unified nomenclature for variants of all five classes of histones that uses consistent but flexible naming conventions to produce names that are informative and readily searchable. The nomenclature builds on historical usage and incorporates phylogenetic relationships, which are strong predictors of structure and function. A key feature is the consistent use of punctuation to represent phylogenetic divergence, making explicit the relationships among variant subtypes that have previously been implicit or unclear. We recommend that by default new histone variants be named with organism-specific paralog-number suffixes that lack phylogenetic implication, while letter suffixes be reserved for structurally distinct clades of variants. For clarity and searchability, we encourage the use of descriptors that are separate from the phylogeny-based variant name to indicate developmental and other properties of variants that may be independent of structure