A new acylphloroglucinol glycoside from Solidago altissima L.

A new acylphloroglucinol glycoside was isolated from the leaves of Solidago altissima L. The chemical structure of the glycoside, which has a phloroglucinol moiety with a butyryl side chain, was elucidated based on the analysis of spectroscopic data.

Phosphorylation of MCM4 by Cdc7 kinase facilitates its interaction with Cdc45 on the chromatin.

Cdc7 kinase, conserved from yeasts to human, plays important roles in DNA replication. However, the mechanisms by which it stimulates initiation of DNA replication remain largely unclear. We have analyzed phosphorylation of MCM subunits during cell cycle by examining mobility shift on SDS-PAGE. MCM4 on the chromatin undergoes specific phosphorylation during S phase. Cdc7 phosphorylates MCM4 in the MCM complexes as well as the MCM4 N-terminal polypeptide. Experiments with phospho-amino acid-specific antibodies indicate that the S phase-specific mobility shift is due to the phosphorylation at specific N-terminal (S/T)(S/T)P residues of the MCM4 protein. These specific phosphorylation events are not observed in mouse ES cells deficient in Cdc7 or are reduced in the cells treated with siRNA specific to Cdc7, suggesting that they are mediated by Cdc7 kinase. The N-terminal phosphorylation of MCM4 stimulates association of Cdc45 with the chromatin, suggesting that it may be an important phosphorylation event by Cdc7 for activation of replication origins. Deletion of the N-terminal non-conserved 150 amino acids of MCM4 results in growth inhibition, and addition of amino acids carrying putative Cdc7 target sequences partially restores the growth. Furthermore, combination of MCM4 N-terminal deletion with alanine substitution and deletion of the N-terminal segments of MCM2 and MCM6, respectively, which contain clusters of serine/threonine and are also likely targets of Cdc7, led to an apparent nonviable phenotype. These results are consistent with the notion that the N-terminal phosphorylation of MCM2, MCM4, and MCM6 may play functionally redundant but essential roles in initiation of DNA replication.

Hsk1 kinase is required for induction of meiotic dsDNA breaks without involving checkpoint kinases in fission yeast.

Cdc7 kinase, conserved through evolution, is known to be essential for mitotic DNA replication. The role of Cdc7 in meiotic recombination was suggested in Saccharomyces cerevisiae, but its precise role has not been addressed. Here, we report that Hsk1, the Cdc7-related kinase in Schizosaccharomyces pombe, plays a crucial role during meiosis. In a hsk1 temperature-sensitive strain (hsk1-89), meiosis is arrested with one nucleus state before meiosis I in most of the cells and meiotic recombination frequency is reduced by one order of magnitude, whereas premeiotic DNA replication is delayed but is apparently completed. Strikingly, formation of meiotic dsDNA breaks (DSBs) are largely impaired in the mutant, and Hsk1 kinase activity is essential for these processes. Deletion of all three checkpoint kinases, namely Cds1, Chk1, and Mek1, does not restore DSB formation, meiosis, or Cdc2 activation, which is suppressed in hsk1-89, suggesting that these aberrations are not caused by known checkpoint pathways but that Hsk1 may regulate DSB formation and meiosis. Whereas transcriptional induction of some rec genes and horsetail movement are normal, chromatin remodeling at ade6-M26, a recombination hotspot, which is prerequisite for subsequent DSB formation at this locus, is not observed in hsk1-89. These results indicate unique and essential roles of Hsk1 kinase in the initiation of meiotic recombination and meiosis.

Rad3-Cds1 mediates coupling of initiation of meiotic recombination with DNA replication. Mei4-dependent transcription as a potential target of meiotic checkpoint.

Premeiotic S-phase and meiotic recombination are known to be strictly coupled in Saccharomyces cerevisiae. However, the checkpoint pathway regulating this coupling has been largely unknown. In fission yeast, Rad3 is known to play an essential role in coordination of DNA replication and cell division during both mitotic growth and meiosis. Here we have examined whether the Rad3 pathway also regulates the coupling of DNA synthesis and recombination. Inhibition of premeiotic S-phase with hydroxyurea completely abrogates the progression of meiosis, including the formation of DNA double-strand breaks (DSBs). DSB formation is restored in rad3 mutant even in the presence of hydroxyurea, although repair of DSBs does not take place or is significantly delayed, indicating that the subsequent recombination steps may be still inhibited. Examination of the roles of downstream checkpoint kinases reveals that Cds1, but not Chk1 or Mek1, is required for suppression of DSB in the presence of hydroxyurea. Transcriptional induction of some rec+ genes essential for DSB occurs at a normal timing and to a normal level in the absence of DNA synthesis in both the wild-type and cds1delta cells. On the other hand, the transcriptional induction of the mei4+ transcription factor and cdc25+ phosphatase, which is significantly suppressed by hydroxyurea in the wild-type cells, occurs almost to a normal level in cds1delta cells even in the presence of hydroxyurea. These results show that the Rad3-Cds1 checkpoint pathway coordinates initiation of meiotic recombination and meiotic cell divisions with premeiotic DNA synthesis. Because mei4+ is known to be required for DSB formation and cdc25+ is required for activation of meiotic cell divisions, we propose an intriguing possibility that the Rad3-Cds1 meiotic checkpoint pathway may target transcription of these factors.

Hsk1-Dfp1/Him1, the Cdc7-Dbf4 kinase in Schizosaccharomyces pombe, associates with Swi1, a component of the replication fork protection complex.

The protein kinase Hsk1 is essential for DNA replication in Schizosaccharomyces pombe. It associates with Dfp1/Him1 to form an active complex equivalent to the Cdc7-Dbf4 protein kinase in Saccharomyces cerevisiae. Swi1 and Swi3 are subunits of the replication fork protection complex in S. pombe that is homologous to the Tof1-Csm3 complex in S. cerevisiae. The fork protection complex helps to preserve the integrity of stalled replication forks and is important for activation of the checkpoint protein kinase Cds1 in response to fork arrest. Here we describe physical and genetic interactions involving Swi1 and Hsk1-Dfp1/Him1. Dfp1/Him1 was identified in a yeast two-hybrid screen with Swi1. Hsk1 and Dfp1/Him1 both co-immunoprecipitate with Swi1. Swi1 is required for growth of a temperature-sensitive hsk1 (hsk1ts) mutant at its semi-permissive temperature. Hsk1ts cells accumulate Rad22 (Rad52 homologue) DNA repair foci at the permissive temperature, as previously observed in swi1 cells, indicating that abnormal single-stranded DNA regions form near the replication fork in hsk1ts cells. hsk1ts cells were also unable to properly delay S-phase progression in the presence of a DNA alkylating agent and were partially defective in mating type switching. These data suggest that Hsk1-Dfp1/Him1 and Swi1-Swi3 complexes have interrelated roles in stabilization of arrested replication forks.

Dermatitis due to epiregulin deficiency and a critical role of epiregulin in immune-related responses of keratinocyte and macrophage.

Epidermal growth factor (EGF) family members, including epiregulin (EP), play a fundamental role in epithelial tissues; however, their roles in immune responses and the physiological role of EP remain to be elucidated. The skin has a versatile system of immune surveillance. Biologically active IL-1alpha is released to extracellular space upon damage from keratinocytes and is a major player in skin inflammation. Here, we show that EP is expressed not only in keratinocytes but also in tissue-resident macrophages, and that EP-deficient (EP(-/-)) mice develop chronic dermatitis. Wound healing in the skin in EP(-/-) mice was not impaired in vivo, nor was the growth rate of keratinocytes from EP(-/-) mice different from that of WT mice in vitro. Of interest is that in WT keratinocytes, both IL-1alpha and the secreted form of EP induced down-regulation of IL-18 mRNA expression, which overexpression in the epidermis was reported to induce skin inflammation in mice, whereas the down-regulation of IL-18 induced by IL-1alpha was impaired in EP(-/-) keratinocytes. Although bone marrow transfer experiments indicated that EP deficiency in non-bone-marrow-derived cells is essential for the development of dermatitis, production of proinflammatory cytokines by EP(-/-) macrophages in response to Toll-like receptor agonists was much lower, compared with WT macrophages, whose dysfunction in EP(-/-) macrophages was not compensated by the addition of the secreted form of EP. These findings, taken together, suggested that EP plays a critical role in immune/inflammatory-related responses of keratinocytes and macrophages at the barrier from the outside milieu and that the secreted and membrane-bound forms of EP have distinct functions.

[Meloxicam (Mobic): a review of its pharmacological and clinical profile].

Meloxicam (Mobic) is a new nonsteroidal anti-inflammatory drug (NSAID) derived from enolic acid, exhibiting selectivity for cyclooxygenase (COX)-2 over COX-1. Meloxicam has shown potent anti-inflammatory and analgesic activity together with low gastrointestinal toxicity in animal models. It is a potent inhibitor not only of acute exudation in adjuvant arthritis in the rat, but also of bone and cartilage destruction. The therapeutic range of meloxicam in the rat, with regard to inhibition of adjuvant arthritis, was several times greater than that of other NSAIDs. Meloxicam in therapeutic doses was found to have no effect on bleeding time or platelet aggregation in healthy volunteers. In clinical studies, meloxicam has shown reliable efficacy against rheumatoid arthritis, osteoarthritis, lumbago (low back pain), scapulohumeral periarthritis, and neck-shoulder-arm syndrome with low gastrointestinal toxicity.