[A case of hepatocellular carcinoma complicated with Caroli's disease].

A 29-year-old man was admitted with right hypochondralgia and fever. Markedly dilated bile ducts were observed, mainly in the right lobe of the liver. Based on both the clinical findings and imaging, we diagnosed Caroli's disease and choledochal cyst complicated with cholangitis. Hepatocellular carcinoma (HCC) was also observed in segment 3, and the tumor measured 4cm in diameter. The patient was successfully treated with hepatectomy of the right lobe, partial hepatectomy of the left lateral lobe, and bile duct reconstruction. A histopathological examination revealed moderately differentiated HCC without any components of cholangiocellular carcinoma (CCC). Although Caroli's disease is complicated with CCC, a case of Caroli's disease complicated with HCC, as in the present case, is quite rare and therefore is considered to be worthy of reporting.

ChlH, the H subunit of the Mg-chelatase, is an anti-sigma factor for SigE in Synechocystis sp. PCC 6803.

Although regulation of sigma factors has been intensively investigated, anti-sigma factors have not been identified in oxygenic photosynthetic organisms. A previous study suggested that the sigma factor, SigE, of the cyanobacterium Synechocystis sp. PCC 6803, a positive regulator of sugar catabolism, is posttranslationally activated by light-to-dark transition. In the present study, we found that the H subunit of Mg-chelatase ChlH interacts with sigma factor SigE by yeast two-hybrid screening, and immunoprecipitation analysis revealed that ChlH associates with SigE in a light-dependent manner in vivo. We also found that Mg(2+) promotes the interaction of SigE and ChlH and determines their localization in vitro. In vitro transcription analysis demonstrated that ChlH inhibits the transcription activity of SigE. Based on these results, we propose a model in which ChlH functions as an anti-sigma factor, transducing light signals to SigE in a process mediated by Mg(2+).

Induction of a group 2 sigma factor, RPOD3, by high light and the underlying mechanism in Synechococcus elongatus PCC 7942.

Among the sigma70 family bacterial sigma factors, group 2 sigma factors have similar promoter recognition specificity to group 1 (principal) sigma factors and express and function under specific environmental and physiological conditions. In general, the cyanobacterial genome encodes more than four group 2 sigma factors, and the unicellular Synechococcus elongatus PCC 7942 (Synechococcus) has five group 2 sigma factors (RpoD2-6). In this study, we analyzed expression of group 2 sigma factors of Synechococcus at both mRNA and protein levels, and we showed that the rpoD3 expression was activated only by high light (1,500 micromol photons m(-2) s(-1)) among the various stress conditions examined. After high light shift, rpoD3 mRNA accumulated transiently within the first 5 min and diminished subsequently, whereas RpoD3 protein increased gradually during the first several hours. We also found that the rpoD3 deletion mutant rapidly lost viability under the same conditions. Analysis of the rpoD3 promoter structure revealed the presence of an HLR1 (high light-responsive element 1) sequence, which was suggested to be responsible for the high light-induced transcription under the control of the NblS (histidine kinase)-RpaB (response regulator) two-component system (Kappell, A. D., and van Waasbergen, L. G. (2007) Arch. Microbiol. 187, 337-342), at +6 to +23 with respect to the transcriptional start site. Here we demonstrated that recombinant RpaB protein specifically bound to HLR1 of the rpoD3 and hliA genes in vitro, and overexpression of a truncated RpaB variant harboring only the phosphoreceiver domain derepressed the transcription in vivo. Thus, we have concluded that phosphorylated RpaB are repressing the rpoD3 and hliA transcription under normal growth conditions, and the RpaB dephosphorylation induced by high light stress results in transcriptional derepression.

Light-responsive transcriptional regulation of the suf promoters involved in cyanobacterium Synechocystis sp. PCC 6803 Fe-S cluster biogenesis.

The widely conserved SUF system is involved in Fe-S cluster repair and biogenesis. In cyanobacterium Synechocystis sp. PCC 6803, transcription of the sufBCDS operon encoding the Suf complex is negatively regulated by the upstream sufR gene encoded by the complementary strand. In this report, two promoters for the sufBCDS operon (P1 and P2) and another promoter for sufR (PsufR) was identified, and it was shown that P1 was activated by a shift to high light conditions. We also showed that Thermosynechococcus SufR negatively regulated P1 and PsufR but not P2, in a reconstituted in vitro transcription system using His(6)-tagged RNA polymerase.

The cyanobacterial principal sigma factor region 1.1 is involved in DNA-binding in the free form and in transcription activity as holoenzyme.

Cyanobacterial principal sigma factor, sigma(A), includes a specifically conserved cluster of basic amino acids in the amino-terminal extension called region 1.1. We found that the sigma(A) in a thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 binds DNA in the absence of the core RNA polymerase and that sigma(A) lacking region 1.1 is not able to bind DNA. This indicates that, in the cyanobacterium, region 1.1 participates in DNA-binding, rather than inhibiting the interaction between free sigma and DNA, as found in other principal sigma factors of eubacteria. The results of in vitro transcription assays with the reconstituted RNA polymerase showed that region 1.1 reduces transcription activity from the cpc promoter.

PF1163A, a novel antifungal agent, inhibit ergosterol biosynthesis at C-4 sterol methyl oxidase.

PF1163A and B are a pair of antifungal agents isolated from a fermentation broth of Penicillium sp. PF1163A inhibited ergosterol synthesis in Saccharomyces cerevisiae, resulting in an accumulation of 4,4-dimethylzymosterol and a decrease of ergosterol. The ERG25 strain overexpressing the ERG25 gene was resistant to PF1163A. ERG25p is a C-4 sterol methyl oxidase known to be essential for the viability of yeast and fungi because of the known role of ERG25 gene disruption in S. cerevisiae-led lethality. ERG25p is the enzyme responsible for the first step in the removal of the two methyl groups at the C-4 position of sterol. From the results obtained here, we conclude that PF1163A is a novel natural antifungal that inhibits C-4 sterol methyl oxidase.