An oncoprotein from the plant pathogen agrobacterium has histone chaperone-like activity

Protein 6b, encoded by T-DNA from the pathogen Agrobacterium tumefaciens, stimulates the plant hormone-independent division of cells in culture in vitro and induces aberrant cell growth and the ectopic expression of various genes, including genes related to cell division and meristem-related class 1 KNOX homeobox genes, in 6b-expressing transgenic Arabidopsis thaliana and Nicotiana tabacum plants. Protein 6b is found in nuclei and binds to several plant nuclear proteins. Here, we report that 6b binds specifically to histone H3 in vitro but not to other core histones. Analysis by bimolecular fluorescence complementation revealed an interaction in vivo between 6b and histone H3. We recovered 6b from a chromatin fraction from 6b-expressing plant cells. A supercoiling assay and digestion with micrococcal nuclease indicated that 6b acts as a histone chaperone with the ability to mediate formation of nucleosomes in vitro. Mutant 6b, lacking the C-terminal region that is required for cell division-stimulating activity and interaction with histone H3, was deficient in histone chaperone activity. Our results suggest a relationship between alterations in nucleosome structure and the expression of growth-regulating genes on the one hand and the induction of aberrant cell proliferation on the other.     

Molecular cloning and characterization of an alpha-amylase from Pichia burtonii 15-1

An alpha-amylase secreted by Pichia burtonii 15-1 isolated from a traditional starter murcha of Nepal, named Pichia burtonii alpha-amylase (PBA), was studied. The gene was cloned and its nucleotide sequence was determined. PBA was deduced to consist of 494 amino acid residues. It shared certain degrees of amino acid sequence identity with other homologous proteins: 60% with Schwanniomyces occidentalis alpha-amylase, 58% with Saccharomycopsis sp. alpha-amylase, and 47% with Taka-amylase A from Aspergillus oryzae. A three-dimensional structural model of PBA generated using the known three-dimensional structure of Taka-amylase A as a template suggested high structural similarity between them. Kinetic analysis revealed that the K(m) values of PBA were lower than those of Taka-amylase A for the oligosaccharides. Although the k(cat) values of PBA were lower than those of Taka-amylase A for the oligosaccharide substrates, the k(cat)/K(m) values of PBA were higher.     

Comparative analysis of enzyme activities and mRNA levels of peptidyl prolyl cis/trans isomerases in various organs of wild type and Pin1-/- mice

We investigated the enzyme activity of peptidyl prolyl cis/trans isomerases (PPIases) in brain, testis, lung, liver, and mouse embryonic fibroblasts (MEF) of Pin1+/+ and Pin1-/- mice. The aim of this study is to determine if other PPIases can substitute for the loss of Pin1 activity in Pin1-/- mice and what influence Pin1 depletion has on the activities of other PPIases members. The results show that high PPIase activities of Pin1 are found in organs that have the tendency to develop Pin1 knockout phenotypes and, therefore, provide for the first time an enzymological basis for these observations. Furthermore we determined the specific activity (k(cat)/K(M)) of endogenous Pin1 and found that it is strongly reduced as compared with the recombinant protein in all investigated organs. These results suggest that posttranslational modifications may influence the PPIase activity in vivo. The activities originating from cyclophilin and FKBP are not influenced by the Pin1 knockout, but a basal enzymatic activity towards phosphorylated substrates could be found in Pin1-/- lysates. Real time PCR experiments of all PPIases in different mouse organs and MEF of Pin1+/+ and Pin1-/- mice support the finding and reveal the specific expression profiles of PPIases in mice.     

A novel type of transposon generated by insertion element Is102 present in a psc101 derivative

We describe a novel type of transposon in the tetracycline resistance plasmid pYM103, a derivative of pSC101 carrying a single copy of an insertion element IS102. The new transposons we found were identified as DNA segments, approximately 6 kb (Tn1021) and 10 kb (Tn1022) in length, able to mediate the cointegration of pYM1O3 with plasmid Col E1. The resulting cointegrate contains either of these pYM1O3 segments duplicated in a direct orientation at the junctions of the parent plasmids. A direct duplication of a 9 bp sequence at the target site in Col E1 is found at the junctions for cointegration. Both transposons have IS1O2 at one end and also contain different lengths of the pYM103 DNA adjacent to IS102, including the tetracycline resistance gene. Each transposon contains terminal inverted repeats of a short nucleotide sequence. These results and the fact that IS102 can itself mediate plasmid cointegration, giving rise to a duplication of a 9 bp target sequence, indicate that IS102 is responsible for generation of Tn1021 and Tn1022. They are quite different from the common IS-associated transposons, which are always flanked by two copies of an IS element, and may be similar to transposons such as those of the Tn3 family and phage Mu.     

Establishment of adipose-derived mesenchymal stem cell lines from a p53-knockout mouse

Mesenchymal stem cells (MSCs) can differentiate into a variety of cell types. MSCs exist in several tissues such as the bone marrow, adipose, muscle, cartilage, and tendon. This differentiation potential makes MSCs candidates for cell-based therapeutic strategies for mesenchymal tissue injuries. MSCs can be prepared from bone marrow (BM-MSCs) and adipose (AD-MSCs); however, these MSCs exhibit senescence-associated growth arrest and display inevitable heterogeneity. We established several AD-MSC cell lines from a p53-knockout (KO) mouse. These cell lines were immortalized, but no cell lines grew anchorage-independently, suggesting that they are not cancerous. They differentiated into adipocytes, osteoblasts, and chondrocytes by treatment with certain stimuli. Moreover, following injection into the tail vein, the cells migrated into the wounded region of the liver and differentiated into hepatocytes. We succeeded in establishing several AD-MSC clonal cell lines that maintain the tissue-specific markers and characteristics of the developmental phase. These clonal cell lines will serve as important tools to study the mechanism of differentiation of MSCs.     

Expression of Notch receptors and ligands on immature and mature T cells

Notch plays multiple roles in T cell development in the thymus and T cell differentiation in the periphery. In order to systematically examine the role of Notch in T cell biology, we determined the cell surface expression of all Notch receptors and ligands on various populations of T cells by using a panel of specific monoclonal antibodies we recently established. Notch1 and Notch3 were upregulated at double-negative (DN) 2-DN4 stages of immature thymocytes, then downregulated on mature single-positive thymocytes and peripheral T cells, but were rapidly upregulated again upon activation. Notch2 was consistently expressed on T cells while Notch4 was not. Jagged1 and Jagged2 were expressed at double-positive stage of immature T cells. Jagged2 was also inducible on mature T cells upon activation. In contrast, no Delta-like (Dll) 1 or Dll4 expression was observed on T cells. These comprehensive profiling of the expression of Notch receptors and ligands would be informative to fully understand the role of individual Notch receptors and ligands in T cell development and differentiation.     

Effect of alendronate on osteoclast differentiation and bone volume in transplanted bone.

Alendronate, one of the bisphosphonates, is known to have an inhibitory effect on bone resorption. The purpose of this study was to investigate the effects of alendronate on ectopic bone graft resorption and to determine the optimal dose in the mouse. The grafted bone in the control group disappeared due to resorption by osteoclasts within 5 weeks. In the experimental groups, the area of bone tissue decreased by only 20-40% at 5 weeks post-operatively. At 8 and 9 weeks after surgery, the decreased area of bone structure was significantly less in all the 10(-4) M injected alendronate-immersed groups than in the 10(-4) M non-injected alendronate-immersed. At 9 weeks after surgery, the number of osteoclasts were significantly less in the 10(-4) M injected alendronate-treated groups than in the 10(-4) M non-injected alendronate-treated groups. These results suggest that alendronate inhibits resorption of ectopic bone graft at concentrations of 10(-4) and 10(-6) M.     

The presence of chemokine receptor (CCR5, CXCR3, CCR3)-positive cells and chemokine (MCP1, MIP-1alpha, MIP-1beta, IP-10)-positive cells in human periapical granulomas.

The infiltration of leukocytes into inflammation sites such as observed in human periapical granulomas is considered to be mediated by chemotactic factors. In this study, we examined the presence of chemokine- and chemokine receptor-positive cells in samples obtained from human subjects by means of immunohistochemical methods. Macrophage chemotactic protein-1 (MCP-1), macrophage inflammatory protein (MIP)-1alpha, MIP-1beta and IFN-inducible protein 10 (IP-10)-producing cells were present in periapical granulomas. In addition, chemokine receptor CCR3-, CCR5-, and CXCR3-positive cells were also present. In contrast, no factor expression was observed in clinically healthy periodontal ligament, serving as a negative control. Our findings suggest that these chemokines are responsible for modulating the process of disease, such as human apical periodontitis.