EGO-1, a Putative RNA-Dependent RNA Polymerase, Is Required for Heterochromatin Assembly on Unpaired DNA during C. elegans Meiosis

During meiosis in C. elegans, unpaired chromosomes and chromosomal regions accumulate high levels of histone H3 lysine 9 dimethylation (H3K9me2), a modification associated with facultative heterochromatin assembly and the resulting transcriptional silencing [1, 2]. Meiotic silencing of unpaired DNA may be a widely conserved genome defense mechanism [3–5]. The mechanisms of meiotic silencing remain unclear, although both transcriptional and posttranscriptional processes are implicated [3–5]. Cellular RNA-dependent RNA polymerases (RdRPs) function in development and RNA-mediated silencing in many species [3, 6, 7] and in heterochromatin assembly in S. pombe [3, 8]. There are four C. elegans RdRPs, including two with known germline functions. EGO-1 is required for fertility and robust germline RNAi [9–11]. RRF-3 acts genetically to repress RNAi and is required for normal meiosis and spermatogenesis at elevated temperatures [12] (S. L’Hernault, personal communication). Among C. elegans RdRPs, we find that only EGO-1 is required for H3K9me2 enrichment on unpaired chromosomal regions during meiosis. This H3K9me2 enrichment does not require Dicer or Drosha nuclease or any of several other proteins required for RNAi. ego-1 interacts genetically with him-17, another regulator of chromatin and meiosis [13], to promote germline development. We conclude that EGO-1 is an essential component of meiotic silencing in C. elegans

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Chemistry of the cambial zone

Title from folder label.Includes Project 1259 summary report dated August 25, 1948.Project report form no. 1 dated August 16, 1946. Report on the research of Ernest Anderson at the Institute of Paper Chemistry during the summer of 1946 --a study of the composition of the inner bark and cambial layer of black spruce / Ernest Anderson -- Project report form no. 2 dated November 1, 1946. Orientating study of the cambial zone of black spruce / L. E. Wise, Evelyn K. Ratliff -- Project report form no. 3 dated November 14, 1946. Investigation of benzene-insoluble extract of black spruce inner bark / W. W. Pigman, B. Thomas -- Project report form no. 4 dated August 5, 1947. This work is concerned with the preparation of sodium calcium galacturonate from pectic acid that Dr. Ernest Anderson had previously isolated from the inner bark of black spruce and with the identification of the sodium calcium galacturonate / Robert L. Leaf, Jr. -- Project report form no. 5 dated August 20, 1947. Report on the research of Ernest Anderson, at the Institute of Paper Chemistry during the summer 1947 / Ernest Anderson -- Project report form no. 6 dated January 13, 1948. Introduction / W. W. Pigman -- Project 1259. Project report form dated August 25, 1948. Summary of the work of Ernest Anderson and Robert Buxton during the summer of 1948 / Ernest Anderson -- Project report form no. 7 dated October 29, 1948. Methylation of the spruce leucoanthocyanin / M. A. Buchanan

Design of SCALES: a 2-5 micron coronagraphic integral field spectrograph for Keck Observatory

editorial reviewedWe present the design of SCALES (Slicer Combined with Array of Lenslets for Exoplanet Spectroscopy) a new 2-5 micron coronagraphic integral field spectrograph under construction for Keck Observatory. SCALES enables low-resolution (R∼50) spectroscopy, as well as medium-resolution (R∼4,000) spectroscopy with the goal of discovering and characterizing cold exoplanets that are brightest in the thermal infrared. Additionally, SCALES has a 12x12" field-of-view imager that will be used for general adaptive optics science at Keck. We present SCALES's specifications, its science case, its overall design, and simulations of its expected performance. Additionally, we present progress on procuring, fabricating and testing long lead-time components