The 2'-5' RNA Ligase of Escherichia coli: Purification, Cloning, and Genomic Disruption

An RNA ligase previously detected in extracts of Escherichia coli is capable of joining Saccharomyces cerevisiae tRNA splicing intermediates in the absence of ATP to form a 2-5 phosphodiester linkage (Greer, C., Javor, B., and Abelson, J. (1983) Cell 33, 899-906). This enzyme specifically ligates tRNA half-molecules containing nucleoside base modifications and shows a preference among different tRNA species. In order to investigate the function of this enzyme in RNA metabolism, the ligase was purified to homogeneity from E. coli lysate utilizing chromatographic techniques and separation of proteins by SDS-polyacrylamide gel electrophoresis. A single polypeptide of approximately 20 kilodaltons exhibited RNA ligase activity. The amino terminus of this protein was sequenced, and the open reading frame (ORF) encoding it was identified by a data base search. This ORF, which encodes a novel protein with a predicted molecular mass of 19.9 kDa, was amplified from E. coli genomic DNA and cloned. ORFs coding for highly similar proteins were detected in Methanococcus jannaschii and Bacillus stearothermophilus. The chromosomal gene encoding RNA ligase in E. coli was disrupted, abolishing ligase activity in cell lysates. Cells lacking ligase activity grew normally under laboratory conditions. However, moderate overexpression of the ligase protein led to slower growth rates and a temperature-sensitive phenotype in both wild-type and RNA ligase knockout strains. The RNA ligase reaction was studied in vitro using purified enzyme and was found to be reversible, indicating that this enzyme may perform cleavage or ligation in vivo

Analysis of TRIP expression in different types of skin tumor

TRAF-interacting protein (TRIP) is a ubiquitously expressed nucleolar E3 ubiquitin ligase. Ubiquitination of proteins is a post-translational modification, which decides on the cellular fate of the protein. TRIP in vivo substrate has not been yet identified. However, TRIP has been shown to play an important role in cellular proliferation, especially in keratinocytes. TRIP was found to be up-regulated in basal cell carcinoma (BCC) at the mRNA level. This prompted us to elucidate its role in skin proliferative diseases such as cancer by analyzing its expression in BCCs at protein level and in squamous cell carcinoma (SCC) at mRNA and protein level. To that purpose, we performed a real-time PCR (qPCR) analysis followed by an immunohistochemistry (IHC) on formalin-fixed, paraffin-embedded (FFPE) biopsies. The real-time PCR was performed on 12 RNA samples of which 6 were extracted from SCC biopsies and 6 from normal human skin. The results were statistically insignificant. Further analyses are needed on new RNA samples. The IHC assay was performed on 20 biopsies from BCCs, 21 biopsies from SCCs and on 5 tissues from normal human skin. The results obtained showed an extensive expression of TRIP in keratinocytes nuclei. Due to various limitations related to the technique and to doubts about preservation of the antigens in the tissues from normal human skin, we could not highlight a clear difference in TRIP expression between the different tissues. In conclusion, further analyses are needed on new RNA samples (qPCR) and on better preserved FFPE tissues from normal skin (IHC) to assess TRIP relative expression in BCCs and SCCs versus normal human skin

On the Economics of Internet Peering

We discuss economic rationales behind peering decisions in the Internet. In We discuss economic rationales behind peering decisions in the Internet. In the first part of the paper we analyze the decision about a bilateral peering agreement between two commercial Internet service providers (ISPs) who are in Cournot competition. In the second part we discuss multilateral peer-ing between commercial ISPs and an academic research network (ARN). The latter is organized as club of academics who share the cost of their net-work. It is discussed whether peering threatens the existence of the ARN and under what circumstances a commercial ISP would want to use strate-gic pricing to win all ARN-members as customers.Internet Economics, Interconnection Agreements

Die Fallstricke einer intentionalistischen Engführung der Geschichtsdeutung

In this commentary I criticise Doris Gerber's intentionalistic reading of history. While an intentionalistic philosophy of history has some plausibility, a *purely* intentionalistic view is often irreconcilable with the most elementary common sense. For example, that history ought to be considered exclusively as the history of human action and not of things that simply happen to humans as well - like the outbreak of the volcano Vesuv in the year 79 which lead to the destructions of Pompeii. Or that historical value judgments should always be judgments about the reasons for human action, which raises the questions if and how the unintended consequences of human action are to be judged

Menorah Review (No. 65, Summer/Fall, 2006)

A Rebbe in Skirts -- By Way of Introduction: Reflections on Israeli Women\u27s Studies: A Reader -- Israeli Literature and Israeli Politics -- More in than Out -- Revisiting Old Themes Through a Contemporary Lens -- The World of Rabbi Nathan -- Noteworthy Book