Diversity of RuBisCO gene responsible for CO2 fixation in an Antarctic moss pillar

Antarctic “moss pillars” are lake-bottom biocenoses that are primarily comprised of aquatic mosses. The pillars consist of distinct redox-affected sections: oxidative exteriors and reductive interiors. Batteries of SSU rRNA genotypes of eukaryotes, eubacteria, and cyanobacteria, but no archaea, have been identified in these pillars. However, rRNA-based phylogenetic analysis provides limited information on metabolic capabilities. To investigate the microorganisms that have the potential for CO₂ fixation in the pillars, we studied the genetic diversity of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO, EC 4.1.1.39)—an enzyme involved in CO₂ fixation. PCR clone libraries targeting all forms of the RuBisCO large subunit-encoding gene were constructed and 1,092 clones were randomly sequenced. Phylogenetic analysis indicated that proteobacterial form IA operational RuBisCO units (ORUs) were detected at the same frequency as the cyanobacterial form IB ORUs. Surprisingly, the form IA ORU, which was closely related to the sequences from deep-sea environments, was detected from all moss pillar sections. The form IB ORU related to Bryophyta, considered to be derived from moss, was identical to the sequence of Leptobryum sp. isolated from Lake Hotoke-Ike where the pillars were found. Moreover, certain cyanobacterial ORUs were found exclusively in the exterior of the pillar, whereas form II ORUs related to chemolithoautotrophic sulfur oxidizers and purple sulfur bacteria were found exclusively in the interior. No forms IC, ID, or III RuBisCO genes were detected. This is the first report demonstrating that bacteria with the potential for CO₂ fixation and chemoautotrophy are present in the Antarctic moss pillar ecosystem.     

The C. elegans CBFbeta homologue BRO-1 interacts with the Runx factor, RNT-1, to promote stem cell proliferation and self-renewal

In this report, we investigate the C. elegans CBFbeta homologue, BRO-1. bro-1 mutants have a similar male-specific sensory ray loss phenotype to rnt-1 (the C. elegans homologue of the mammalian CBFbeta-interacting Runx factors), caused by failed cell divisions in the seam lineages. Our studies indicate that BRO-1 and RNT-1 form a cell proliferation-promoting complex, and that BRO-1 increases both the affinity and specificity of RNT-1-DNA interactions. Overexpression of bro-1, like rnt-1, leads to an expansion of seam cell number and co-overexpression of bro-1 and rnt-1 results in massive seam cell hyperplasia. Finally, we find that BRO-1 appears to act independently of RNT-1 in certain situations. These studies provide new insights into the function and regulation of this important cancer-associated DNA-binding complex in stem cells and support the view that Runx/CBFbeta factors have oncogenic potential.     

Intra-specific composition and succession of Bifidobacterium longum in human feces

Intra-species analysis of pulsed field gel electrophoresis (PFGE) on human fecal Bifidobacterium longum isolates revealed that a majority of 12 Japanese subjects harbored strains of unique PFGE types or subtypes over a 68-week period, suggesting that "indigenous"Bifidobacterium strains remain stable for a considerable time in each individual intestinal microbiota.     

Characterization of sexual reproductive processes in Chara braunii (Charales,Charophyceae)

Chara braunii is distributed worldwide and is the most common charalean species in Japan. This species is monoecious and produces numerous sets of sex organs, each of which consists of one antheridium and one oogonium, under laboratory culture conditions. In this study, we report that light intensity strongly affected the vegetative phase and sexual reproductive phase of this species. Under high‐light conditions (70.0 μmol photons m^?2 s^?1), thalli grew but did not form reproductive organs. Under a low‐light intensity (10.0 μmol photons m^?2 s^?1), algal bodies formed many reproductive organs. In addition, antheridia without the corresponding oogonia (lone antheridia) were observed under low‐light conditions. The absence of oogonium primordia adjacent to the lone antheridium was confirmed by several microscopic approaches. The addition of liquid fertilizer increased the total number of sex organs and growth; however, the number of lone antheridia decreased with increasing fertilizer concentrations. Exogenously applied gibberellin did not affect the number of lone antheridia. These results suggest that regulatory mechanisms for the appropriate allocation of resources exist in this alga, similar to those reported in some land plants.     

A quantitative method for analyzing establishing-efficiency of persistent viral infection

A quantitative method for analyzing establishing-efficiency of persistent infection was devised. The efficiency of hPIV2 CA and SV5 T1 strains was found to be high, that is, 0.1∼0.3 (an efficiency of 1.0 indicates that 100% of the virus-infected cells became persistently infected). The efficiency of the SV5 WR strain was also high, approximately 0.1, though the virus had no ability to immediately establish a steady state of persistent infection in whole cell-culture systems. At about 0.0007, the efficiency of SV41 was almost the same as that of the hPIV2 Toshiba strain. The establishing efficiencies of various rSeV were further analyzed in detail. The efficiencies of the rSeV(PA), rSeV(Ppi) and rSeV(HNpi) were below the limit of detection, while that of rSeV(Lpi) was nearly 1. Although the efficiency was around 0.001, the rSeV(Mpi) and the rSeV(Fpi) were unexpectedly found to be capable of forming persistently-infected cells, indicating that both the Fpi and Mpi proteins contribute to the establishing efficiency of persistent infection of SeVpi.     

Aneuploidy in immortalized human mesenchymal stem cells with non-random loss of chromosome 13 in culture

Aneuploidy (an abnormal number of chromosomes) is commonly observed in most human cancer cells, highlighting the need to examine chromosomal instability in tumorigenesis. Previously, the immortalized human mesenchymal stem cell line UE6E7T-3 was shown to undergo a preferential loss of one copy of chromosome 13 after prolonged culture. Here, the loss of chromosome 13 was found to be caused by chromosome missegregation during mitosis, which involved unequal segregation, exclusion of the misaligned chromosome 13 on the metaphase plate, and trapping of chromosome 13 in the midbody region, as observed by fluorescence in situ hybridization. Near-diploid aneuploidy, not tetraploidy, was the direct result. The loss of chromosome 13 was non-random, and was detected by analysis of microsatellites and single nucleotide polymorphism-based loss of heterozygosity (LOH). Of the five microsatellite loci on chromosome 13, four loci showed microsatellite instability at an early stage in culture, and LOH was apparent at a late stage in culture. These results suggest that the microsatellite mutations cause changes in centromere integrity provoking loss of this chromosome in the UE6E7T-3 cell line. Thus, these results support the use of this cell line as a useful model for understanding the mechanism of aneuploid formation in cell cultures.     

Seamounts, New Moon and eel Spawning: The Search for the Spawning Site of the Japanese eel

After analyzing all the collection data for larvae of the Japanese eel, Anguilla japonica, in the western North Pacific, we found that the spawning site of this species appears to be near three seamounts in the West Mariana Ridge, 2000–3000km away from their freshwater habitats. These seamounts are located in the westward flow of the North Equatorial Current and are hypothesized to provide cues for migrating silver eels and to serve as possible aggregation sites for spawning. Back-calculated birth dates based on otolith microstructure of leptocephali indicate that the Japanese eel does not spawn continuously during the long spawning season from April to November, but is synchronized to spawn periodically once a month during new moon. This lunar periodicity of spawning and the seamount spawning hypothesis are new developments in the millennium-old mystery of eel spawning that has fascinated naturalists since the time of Aristotle.     

Hsp90 inhibitors suppress HCV replication in replicon cells and humanized liver mice

Persistent infection with hepatitis C virus (HCV) is a major cause of liver diseases such as chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. Here we report that inhibition of heat shock protein 90 (Hsp90) is highly effective in suppressing HCV genome replication. In HCV replicon cells, HCV replication was reduced by Hsp90 inhibitors and by knockdown of endogenous Hsp90 expression mediated by small-interfering RNA (siRNA). The suppression of HCV replication by an Hsp90 inhibitor was prevented by transfection with Hsp90 expression vector. We also tested the anti-HCV effect of Hsp90 inhibition in HCV-infected chimeric mice with humanized liver. Combined administration of an Hsp90 inhibitor and polyethylene glycol-conjugated interferon (PEG-IFN) was more effective in reducing HCV genome RNA levels in serum than was PEG-IFN monotherapy. These results suggest that inhibition of Hsp90 could provide a new therapeutic approach to HCV infection.