Nucleic acids research. Supplement (2001)最新文献

Properties of the DNA containing the (6-4) photoproduct, one of the major UV-induced lesions, were analyzed. Two basic studies towards artificial recognition and repair of this type of damaged DNA are presented here. One is recognition of the UV-damaged DNA by a minor groove-binding drug. It was found by CD spectroscopy that distamycin could bind DNA duplexes containing the (6-4) photoproduct as effectively as the unmodified DNA, whereas a DNA duplex containing the cyclobutane pyrimidine dimer was not recognized by this drug. The other is a mechanistic study on alkali degradation of this photoproduct. HPLC and NMR analyses revealed that hydrolysis between the N3 and C4 positions of the 5' pyrimidine component occurred first. This intermediate was relatively stable, and further degradation to the strand break required severe conditions like the hot piperidine treatment.

Expression of a number of genes encoding enzymes involved in phospholipid biosynthesis in yeast Saccharomyces cerevisiae is known to be repressed on the addition of myo-inositol and choline to the culture medium (inositol-choline regulation). All genes subject to this inositol-choline regulation have an octamer sequence 5'-CATRTGAA-3' in their upstream regions and those octamer sequences play an important role in this regulation. To confirm the role of the octamer sequence further, we studied the transcriptional regulation of two distinct S-adenosylmethionine synthetase genes (SAM1 and SAM2) of S. cerevisiae. Quantitative RT-PCR analysis showed that only the SAM2 gene was subject to the inositol-choline regulation, consistent with the fact that only the SAM2 gene has two octamer sequences in its upstream region. Furthermore, functional promoter analysis revealed that the proximal octamer sequence of the SAM2 gene has an essential role for this regulation.

Telomere-mimic carbocyclic 5'-nor 3'-deoxyoligonucleotide was synthesized. And it's selectivity to RNA was shown.

To investigate the mechanism underlying the photoreaction of bromouracil in DNA, a detailed analysis of photoirradiated 5'-d(CGCG(Br)UGCG)-3'/5'-d(C(8MeO)GCAC(m)GCG)-3' was undertaken. We found that rG- and 2-aminoimidazolone-containing octanucleotides are formed efficiently in Z-form DNA. These results suggest that interstrand electron transfer initiates the photoreaction of bromouracil in Z-DNA.

Eukaryotic tRNAs are transcribed, processed and exported from the nucleus to the cytoplasm to participate in protein biosynthesis. A variant of human gene for tRNA(Val), HtV4, is not processed neither its 5'- nor its 3'-flanking sequences. By RT-PCR analysis and in situ hybridization, we demonstrated that the HtV4 was constitutively expressed without processing, and localized in the nucleus in HeLa cells.

Isolation of the designated genome region of Bacillus subtilis was investigated using a B. subtilis recombinational transfer (BReT) system. Two DNA sequences flanking the precise genome region are cloned in the BReT vector. The BReT plasmid recovered the predicted genome sequence as large as 100 kb with high fidelity. The result indicates that the BReT system originally developed to recover the non-cognate segments cloned in the B. subtilis genome vector can be applied to the cognate sequence.

Effective photo-regulation of transcription reaction by SP6 RNA polymerase (RNAP) was achieved with photo-responsive SP6 promoter tethering two azobenzenes. With one azobenzene in either TATA or RNAP binding region of the SP6 promoter, photo-regulation activity was very small. But when two azobenzenes were introduced into both regions, efficient photo-regulation of transcription was attained: transcription proceeded 3.5 fold faster under UV irradiation than under dark.

5-Hydroxyuracil (HOU) and 5-hydroxycytosine (HOC) are major oxidative lesions of cytosine with mutagenic potentials. Therefore, HOU and HOC need to be removed from DNA to avoid mutation. In this study, oligonucleotide substrates containing HOU and HOC were synthesized by DNA polymerase reactions and tested for DNA glycosylases. Ung exhibited an extremely low activity for HOU as compared to uracil (U). In contrast, hSMUG1 excised HOU and U with a comparable efficiency. Ung and hSMUG1 did not excise HOC.

The RNA subunit of bacterial ribonuclease P (RNase P) is a ribozyme which can cleave a canonical cloverleaf tRNA precursor and a hairpin RNA with a CCA-3' tag sequence as its substrate. At high concentration of Mg ion, the substrate shape preference of the ribozyme becomes broader to accept a hairpin shape RNA. In hairpin RNA cleavage reactions, we found that the base interaction between the base U294 of E. coli ribozyme and the base N73 of the substrate RNA did not obey the response according to the Watson-Crick type interaction which is usually observed in the interaction between the base U294 of ribozyme and the base N73 of tRNA precursor.

3'-Fluoro analogue 1 of selective and potent adenosine A3 receptor agonist, Cl-IB-MECA was synthesized from D-xylose via highly regioselective opening of lyxo-epoxide 4 with fluoride anion. Compared to the high binding affinity of Cl-IB-MECA to the A3 adenosine receptor, the corresponding 3'-fluoro derivative showed remarkably decreased binding affinity, indicating that 3'-hydroxyl group acts as hydrogen bonding donor, not hydrogen bonding acceptor like fluorine atom in binding to the A3 adenosine receptor.