In Vivo Expression of MHC Class I Genes Depends on the Presence of a Downstream Barrier Element

Regulation of MHC class I gene expression is critical to achieve proper immune surveillance. In this work, we identify elements downstream of the MHC class I promoter that are necessary for appropriate in vivo regulation: a novel barrier element that protects the MHC class I gene from silencing and elements within the first two introns that contribute to tissue specific transcription. The barrier element is located in intergenic sequences 3′ to the polyA addition site. It is necessary for stable expression in vivo, but has no effect in transient transfection assays. Accordingly, in both transgenic mice and stably transfected cell lines, truncation of the barrier resulted in transcriptional gene silencing, increased nucleosomal density and decreased histone H3K9/K14 acetylation and H3K4 di-methylation across the gene. Significantly, distinct sequences within the barrier element govern anti-silencing and chromatin modifications. Thus, this novel barrier element functions to maintain transcriptionally permissive chromatin organization and prevent transcriptional silencing of the MHC class I gene, ensuring it is poised to respond to immune signaling

Direct sequencing of PCR-amplified junction fragments from tandemly repeated transgenes.

When microinjected foreign genes integrate into the genomes of mice, multiple copies are frequently found clustered together at one location. How they concatamerize--by the integration of large linearized concatamers that are formed by simple end-to-end linkage, by circularization of individual DNA fragments and recombination, or by some other means--is not understood. In the transgenic animals studied thus far by ourselves and others, integration frequency and transgene copy number do not seem to be significantly influenced by the complementarity of the ends of the DNA fragments that have been microinjected. We have utilized PCR amplification and DNA sequence analysis to study selected transgene junctions at the nucleotide level. In two transgenic mice carrying the synthetic RSVcat gene (injected with noncomplementary overhangs on the fragment ends), ends were 'nibbled' from 1 to 62 bases before being joined to an adjacent gene copy. Repeated dinucleotides, providing the most minimal of homologies, are present in half of the characterized junctions. Determination of the relative copy number of the junctions in each mouse supports the idea that transgene complexes can undergo additional rearrangements after the initial formation event

Developmentally regulated, low abundance Tec element transcripts in Euplotes crassus--implications for DNA elimination and transposition.

During macromolecular development in the ciliated protozoan, Euplotes crassus, > 105 Tec elements are precisely eliminated from the genome in a 2-4 h time interval, generating extrachromosomal circular forms of the elements. Various models have proposed a transposition-based mechanism for this excision. We have tested this hypothesis by determining the abundance of transcripts of Tec element open reading frames (ORFs) and the timing of their appearance. Transcripts are very low in abundance and are only detected by PCR amplification techniques. Thus, the low levels of transcripts argue against the participation of element-encoded functions in the Tec element elimination process. The element transcripts are only detected in RNA samples from mated cells, indicating that the micronucleus and/or developing macronucleus are transcriptionally active during the sexual phase of the life cycle. The transcription detected could allow a low level of germline-specific transposition for these elements

Hamburger Luftmessnetz. Ergebnisse fuer die Jahre 1991-1995

Das Hamburger Luftmessnetz erfasst seit 1984 die Schadstoffgehalte der Hamburger Luft mit Hilfe von automatischen Analysatoren. Hierbei werden vor allem die Luftschadstoffe Schwefeldioxid (SO_2), Stickstoffoxid (NO_2), Stickstoffmonoxid (NO), Kohlenmonoxid (CO), Schwebstaub, Ozon (O_3), Gesamtkohlenwasserstoff ohne Methan (CnHm) gemessen. Seit dem 01. Februar 1995 wurde an einer Strassenmessstation Russ kontinuierlich gemessen. Benzol, Toluol und Xylol und Russ wurden ausserdem im Rahmen der strassenbezogenen Messungen diskontinuierlich erfasst. An drei Messstationen wurden die meteorologischen Kenngroessen Temperatur, Luftfeuchte, Windrichtung und Windgeschwindigkeit ermittelt. (orig.)The Hamburg air measurement network has been collecting the contents of harmful substances in Hamburg's air since 1984, with the aid of automatic analysers. In this, above all the harmful air substances sulphur dioxide (SO_2), nitrogen dioxide (NO_2), nitrogen monoxide (NO), carbon monoxide (CO), subspended dust, ozone (O_3) and total hydrocarbons excluding methane (C_nH_m) are measured. Since February 1st 1995, soot was continuously measured at one street measuring station. Benzol, toluol and xylol and also soot are also discontinuously measured in the street measurements. The meteorological parameters of temperature, humidity of the air, wind direction and wind speed were determined at three measuring stations. (orig.)Available from TIB Hannover: RO 4305(53) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman