M. Tromp

Major transcript of the frameshifted coxII gene from trypanosome mitochondria contains four nucleotides that are not encoded in the DNA

The mitochondrial cytochrome oxidase (cox) subunit II gene from trypanosomes contains a frameshift at amino acid 170. This gene is highly conserved in different trypanosome species, suggesting that it is functional. Sequence determination of coxII transcripts of T. brucei and C. fasciculata reveals four extra, reading frame-restoring nucleotides at the frameshift position that are not encoded in the DNA. Southern blot analysis of DNA of both trypanosome species failed to show the existence of a second version of the coxII gene. We conclude, therefore, that the extra nucleotides are added during or after transcription of the frameshift gene by an RNA-editing process.

A convenient and general approach to the synthesis of properly protected d-nucleoside-3′-hydrogenphosphonates via phosphite intermediates

Abstract Evidence will be presented to show that the monofunctional phosphitylating reagents bis(N,N-di-ethylamino)chlorophosphine and salicylchlorophosphine are very effective for the preparation of 5′-0,N-protected d-nucleoside-3′-hydrogenphosphonates.

Virus-induced synthesis of messenger RNAs for precursors of pathogenesis-related proteins in tobacco

Infection of Samsun NN tobacco with tobacco mosaic virus (TMV) induces a number of host‐encoded, so‐called pathogenesis‐related (PR‐) proteins, which are found in the intercellular space of the leaf and are associated with induced resistance. By immunoprecipitation of their in vitro translation products we were able to detect the mRNAs corresponding to a number of PR‐proteins in TMV‐infected tobacco, but not in healthy plants. Analysis by the Northern blot technique using cloned cDNA of PR1‐mRNAs as probe showed that the mRNAs for the closely related proteins PR1a, 1b and 1c occur at a low level in healthy tobacco; upon TMV infection this level is increased >100‐fold. The PR1‐specific probe did not hybridize to mRNAs corresponding to other PR‐proteins. Sequencing of the 5′‐terminal region of PR1‐mRNAs showed that PR1‐proteins are derived from precursors by removal of an N‐terminal signal peptide of 30 amino acids.

A new and versatile approach to the preparation of valuable deoxynucleoside 3′-phosphite intermediates

Abstract The easily accessible and crystalline monofunctional phosphitylating reagent bis-(diisopropylamino) chlorophosphine has been used for the synthesis of phosphoramidites and H-phosphonates of d-nucleosides and, also, the formation of 3′-5′-internucleotidic phosphonate bonds.

Adenovirus DNA replication in vitro: site-directed mutagenesis of the nuclear factor I binding site of the Ad2 origin.

The template requirements for efficient adenovirus DNA replication were studied in vitro in a reconstituted system with cloned DNA fragments, containing the Ad2 origin region, as templates. Replication is enhanced by nuclear factor I, a cellular protein that binds specifically to the Ad2 origin. This stimulation is shown to be strongly dependent on the concentration of the adenovirus DNA binding protein. Using synthetic oligonucleotides we have constructed plasmids with base substitutions in the nuclear factor I binding region. Footprint analysis and competition filter binding studies show that two of the three small blocks of conserved nucleotides in this region are involved in the binding of nuclear factor I. The binding affinity can be influenced by the base composition of the degenerate region just outside these two blocks. In vitro initiation and DNA chain elongation experiments with the mutants demonstrate that binding of nuclear factor I to the Ad2 origin is necessary for stimulation. However, binding alone is not always sufficient since a mutation which only slightly disturbs binding is strongly impaired in stimulation of DNA replication by nuclear factor I.

A Convenient and General Approach to the Synthesis of Properly Protected d-Nucleoside-3′-hydrogenphosphonates via Phosphite Intermediates.

Aus den Nucleosiden (I) entstehen mit dem Salicyl-chlorphosphit (II) die Substitutionsprodukte (III), die mit Pyridin/ Wasser zu den Phosphonaten (IV) reagieren.