Site-specificity of histone H1 methylation by two H1-specific protein-lysine N-methyltransferases from Euglena gracilis

1. The histone H1 fractions from rat spleen and liver were used as substrates for two H1-specific protein-lysine N-methyltransferases, V-A and V-B (protein methylase III) from Euglena gracilis. 2. When the enzymatically [methyl-3H]labeled H1 fractions were resolved by two-dimensional gel electrophoresis, four subtypes were found to be methylated (H1b, H1c, H1d and H1e). Both enzymes methylated H1c and H1b to approximately the same extent; H1d and H1e were methylated preferentially by enzyme V-B and V-A, respectively. 3. Histone H1c, [methyl-3H]labeled by the methyltransferase V-A, which had been digested by arginine-specific protease (Arg C protease), showed a single radioactive peptide on HPLC, indicating methylation site specificity of the enzyme. 4. Arg C protease-digestion of [methyl-3H]labeled H1c labeled by methyltransferase V-B indicated that this enzyme methylated two sites on the histone molecule. 5. The histone H1c methylation sites of these two enzymes did not overlap, indicating the two enzymes have different site specificity. 6. In combination with the other results, this suggests that the two enzymes serve discrete purposes, possibly involving the presumed different actions of histone H1 subtypes.     

Effect of enzymatic methylation of apocytochrome c on holocytochrome c formation and proteolysis

1. Methylation of the lysine at residue 72 of yeast apocytochrome c increases its import into mitochondria. 2. Using methylated and unmethylated apocytochrome c as substrate and intact yeast mitochondria and a solubilized mitochondrial fraction as a source of cytochrome c heme lyase, the results show that the methylation state of the apoprotein has no significant effect on its conversion to holoprotein. 3. The above result suggests that the import mechanism is separate from the heme-attaching activity. 4. Unmethylated apocytochrome c was less resistant to a yeast homogenate fraction that methylated apocytochrome c, suggesting that methylation of apocytochrome c alters the conformation of the whole protein.     

New mutations fts-36, lts-33, and ftsW clustered in the mra region of the Escherichia coli chromosome induce thermosensitive cell growth and division.

Three new mutants of Escherichia coli showing thermosensitive cell growth and division were isolated, and the mutations were mapped to the mra region at 2 min on the E. coli chromosome map distal to leuA. Two mutations were mapped closely upstream of ftsI (also called pbpB), in a region of 600 bases; the fts-36 mutant showed thermosensitive growth and formed filamentous cells at 42 degrees C, whereas the lts-33 mutant lysed at 42 degrees C without forming filamentous cells. The mutation in the third new thermosensitive, filament-forming mutant, named ftsW, was mapped between murF and murG. By isolation of these three mutants, about 90% of the 17-kilobase region from fts-36-lts-33 to envA could be filled with genes for cell division and growth, and the genes could be aligned.     

Double-stranded RNA unwinding and modifying activity is detected ubiquitously in primary tissues and cell lines.

A double-stranded RNA unwinding and modifying activity was found to be present in a wide range of tissues and cell types. The level of activity did not vary significantly with respect to the state of cell differentiation, cell cycle, or transformation. Thus, the unwinding and modifying activity, localized in the nucleus in somatic cells and capable of converting many adenosine residues to inosine, appears to be one of the housekeeping genes.     

Albumin — vitamin D-binding protein haplotypes in Asian-Pacific populations

Summary We have determined the various haplotypic combinations between alleles as well as restriction fragment length polymorphisms of two linked genetic markers, albumin and vitamin D-binding protein or group-specific component, in a number of Asian-Pacific populations. Using the partial maximum likelihood method, we constructed a phylogenetic network from the haplotype frequencies to assess relationships among the populations sampled. No systematic linkage disequilibrium was detected between most of the combinations, suggesting a lack of operation of any selection pressure at the two loci. The phylogenetic analysis confirmed the known interrelationships among various populations in the Asian-Pacific region. The Australian aborigines clustered closely with the non-Austronesian-speaking highlanders from Papua New Guinea, as expected. Similarly, the Austronesian-speaking Polynesians, Micronesians, and the Southeast Asians branched off together as a separate group. The position of the Austronesian-speaking Tolais from New Britain with respect to other populations from the Southwest Pacific was anomalous. The Tolais revealed a strong affinity with the Australian aborigines, which is inexplicable. The populations from China formed a tight cluster with other populations from the Asian-Pacific region. Genetic interrelationships of these populations with the white Australians were remote, which is in accordance with the known affinities of various human racial groups.     

The effect of ranitidine on cellular immunity in patients with multiple myeloma

Summary Multiple myeloma is characterized by an increased susceptibility to infections and to other malignancies. In a double-blind, placebo-controlled study the potential impact of immunomodulation by ranitidine was studied in 20 patients with multiple myeloma. Three patients were untreated, while 17 after previous cytotoxic therapy were in a stable phase of their disease. All were without clinical signs of infections and at that time had not been treated with other immunomodulating agents. The patients were randomized to oral ranitidine 300 mg twice a day for 21 days or placebo, and several immunological parameters related to multiple myeloma were studied. The blood monocyte chemotactic response was improved in patients treated with ranitidine, and superoxide anion production increased from 2.02 nmol/min to 3.86 nmol/min (median values), while it was unchanged in patients given placebo (2.19–2.25 nmol/min) (P <0.005 between groups). Among ranitidine-treated patients spontaneous NK cell activity was unchanged, while in vitro interleukin-2- and interferon--stimulated NK cell activity decreased (P <0.03, respectively). As production of oxygen radicals constitutes an important mechanism of monocyte killing activity against microorganisms and probably against malignant cells, it is suggested that ranitidine may be of beneficial impact in the treatment of multiple myeloma.