Identification of the mouse paternally expressed imprinted gene Zdbf2 on chromosome 1 and its imprinted human homolog ZDBF2 on chromosome 2

In mammals, both the maternal and paternal genomes are necessary for normal embryogenesis due to parent-specific epigenetic modification of the genome during gametogenesis, which leads to non-equivalent expression of imprinted genes from the maternal and paternal alleles. In this study, we identified a paternally expressed imprinted gene, Zdbf2, by microarray-based screening using parthenogenetic and normal embryos. Expression analyses showed that Zdbf2 was paternally expressed in various embryonic and adult tissues, except for the placenta and adult testis, which showed biallelic expression of the gene. We also identified a differentially methylated region (DMR) at 10 kb upstream of exon 1 of the Zdbf2 gene and this differential methylation was derived from the germline. Furthermore, we also identified that the human homolog (ZDBF2) of the mouse Zdbf2 gene showed paternal allele-specific expression in human lymphocytes but not in the human placenta. Thus, our findings defined mouse chromosome 1 and human chromosome 2 as the loci for imprinted genes.     

Studies on Transglycosidation to Vitamin B6 by Microorganisms

Some properties of pyridoxine glucoside-synthesizing enzyme were studied using the partially and highly purified enzyme preparations from Micrococcus sp. No. 431.

The enzyme was stable at pH 7.0 and between 0°C and 30°C. The maximal activity was obtained at pH 8.0 and 37°C. Besides sucrose, phenyl-α-d-glucoside and maltose served as glucosyl donor. Of vitamin B₆ compounds tested, only pyridoxine served as glucosyl acceptor. The enzyme activity was inhibited by PCMB and heavy metal ions, and the inhibition was prevented by 2-mercaptoethanol, indicating the enzyme would be a sulfhydryl enzyme. The activity was not affected by chelating agents and not activated by metal ions.     

Ricin and alpha-sarcin alter the conformation of 60S ribosomal subunits at neighboring but different sites

The effects of ricin and alpha-sarcin separately or in combination on the conformation of rat liver ribosomes were investigated by measuring the relative accessibility of individual ribosomal proteins to N-ethylmaleimide after 80S ribosomes were treated with these toxins. By using a double-labelling technique in which ribosomes were incubated with the toxins and then treated with 3H-labelled or 14C-labelled N-ethylmaleimide, it was found that labelling of protein L14 was specifically reduced by treatment with ricin, and that of proteins L3 and L4 by treatment with alpha-sarcin, suggesting that the toxins alter the conformation of ribosomes in the vicinity of these proteins. When ribosomes were treated with both ricin and alpha-sarcin, the extent of labelling of protein L3 was reduced compared to that observed after treatment with alpha-sarcin alone. These results are discussed in relation to previous observations showing that these three proteins are neighbours in the 60S ribosomal subunit and probably play important roles in protein biosynthesis, and in the actions of ricin and alpha-sarcin on 28S rRNA.     

Metabolisms of Nucleosides in Bacteria

In this study, the authors developed a simplified method for the separation and the quantitative determination of nucleosides and bases, using paper electraophoretic technique. By this method, nucleosides and bases were well separated and determined in a fairly short time. Thus, this method was expected to be as accurate as the published methods and was believed to be a better method for both quantitative determination and detection of the nucleosides and bases in a large number of samples.