Translation termination depends on the sequential ribosomal entry of eRF1 and eRF3.

Translation termination requires eRF1 and eRF3 for polypeptide-and tRNA-release on stop codons. Additionally, Dbp5/DDX19 and Rli1/ABCE1 are required; however, their function in this process is currently unknown. Using a combination of in vivo and in vitro experiments, we show that they regulate a stepwise assembly of the termination complex. Rli1 and eRF3-GDP associate with the ribosome first. Subsequently, Dbp5-ATP delivers eRF1 to the stop codon and in this way prevents a premature access of eRF3. Dbp5 dissociates upon placing eRF1 through ATP-hydrolysis. This in turn enables eRF1 to contact eRF3, as the binding of Dbp5 and eRF3 to eRF1 is mutually exclusive. Defects in the Dbp5-guided eRF1 delivery lead to premature contact and premature dissociation of eRF1 and eRF3 from the ribosome and to subsequent stop codon readthrough. Thus, the stepwise Dbp5-controlled termination complex assembly is essential for regular translation termination events. Our data furthermore suggest a possible role of Dbp5/DDX19 in alternative translation termination events, such as during stress response or in developmental processes, which classifies the helicase as a potential drug target for nonsense suppression therapy to treat cancer and neurodegenerative diseases

Jahresbericht 1998 aus dem Messnetz des Umweltbundesamtes

Die Ergebnisse aus dem Messnetz des Umweltbundesamtes werden erstmals in Form eines Jahresberichtes fuer das Jahr 1998 vorgestellt, diskutiert und mit Messungen aus fruehreren Jahren verglichen. Das UBA-Messnetz besteht heute aus insgesamt 23 in laendlichen Gebieten gelegenen Stationen, wovon 9 Messstellen personell besetzt und 14 automatisch arbeitende Containerstationen sind. Als generelles Fazit laesst sich feststellen, dass sich die Luftqualitaet an den Stationen in den neuen und alten Bundeslaendern seit der Wiedervereinigung einander angeglichen hat. Waehrend die Konzentrationen von SO_2 in den neuen Bundeslaendern seit 1990 stark abgenommen haben und sich dem sehr niedrigen Niveau in den alten Bundeslaendern annaehern, haben andere Luftverunreinigungen wie etwa NO_x und O_3 hauptsaechlich wegen der starken Zunahme des Verkehrs in den neuen Bundeslaendern leicht zugenommen, so dass heute etwa das gleiche Konzentrationsniveau in den alten und neuen Bundeslaendern erreicht ist. Auch beim sauren Regen werden heute etwa die gleichen Konzentrationen der Ionen an den Stationen des UBA-Messnetzes in den alten und neuen Bundeslaendern beobachtet. (orig.)For the first time the results of the air pollution monitoring network of the German Federal Environmental Agency (FEA) are presented as an annual report beginning with the year 1998. The network consists of 23 stations (9 stations with personal and 14 automatically working container stations) which are situated in rural areas. Summarizing the results of this report it can be stated that air quality for a series of pollutants has approached a similar level in eastern and western Germany since 1990. (orig.)Available from TIB Hannover: RN 8422(1999,66) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

European surface ozone in the extreme summer 2003

Measurements of ozone and other trace species in the European EMEP network in 2003 are presented. The European summer of 2003 was exceptionally warm and the surface ozone data for central Europe show the highest values since the end of the 1980s. The 99 percentiles of daily maximum hourly ozone concentrations in 2003 was higher than the corresponding parameter measured in any previous year at many sites in France, Germany, Switzerland and Austria. In this paper we argue that a number of positive feedback effects between the weather conditions and ozone contributed to the elevated surface ozone. Firstly we calculated an extended residence time of air parcels in the atmospheric boundary layer for several sites in central Europe. Secondly we show that it is likely that extensive forest fires on the Iberian Peninsula, resulting from the drought and heat, contributed to the peak ozone values in North Europe in August. Thirdly, regional scale model calculations indicate that biogenic isoprene could have contributed with 20% of the peak ozone concentrations. Measurements indicate elevated concentrations of isoprene compared to previous years. Sensitivity runs with a global chemical transport model showed that a reduction in the surface dry deposition due to drought and the elevated air temperature both could have contributed significantly to the enhanced ozone concentrations. Due to climate change, situations like this may occur at a higher frequency in the future and may gradually overshadow the effect of reduced emissions from anthropogenic sources of VOC and NOx

European surface ozone in the extreme summer 2003

International audienceMeasurements of ozone and other species from the European EMEP network in 2003 are presented. The European summer of 2003 was exceptionally warm and the surface ozone data for central Europe show the highest values since the end of the 1980s. The concentrations were particularly high in June and August 2003. In this paper we argue that a number of positive feedback effects between the weather conditions and ozone contributed to the elevated surface ozone. Firstly, direct measurements of isoprene as well as the increased temperature and solar radiation indicate that biogenic emissions in Europe were increased during summer 2003 with a potential for enhanced ozone formation. Secondly, we show that the anticyclonic conditions during the ozone episodes were accompanied by an extended residence time of air parcels in the atmospheric boundary layer, a low total ozone column and a reduced cloud cover, all favouring ozone formation. Thirdly, based on the Lagrangian dispersion model FLEXPART, we show that is very likely that extensive forest fires on the Iberian Peninsula, resulting from the drought and heat, contributed to the peak ozone values observed in North Europe in August. Additionally, forest fires in Siberia probably lead to an elevated background level of ozone and CO at northern latitudes during summer 2003 thereby increasing the level the peak ozone episodes sat on. Lastly, and most important, the heat wave presumably lead to less efficient ozone dry deposition due to stomata closure of the plants under drought stress. Due to climate change, situations like this may occur at a higher frequency in the future and may gradually overshadow the effect of reduced emissions from anthropogenic sources of VOC and NOx. This scenario also holds for secondary PM