Analysis of Cre1 binding sites in the Trichoderma reesei cbh1 upstream region

Abstract A 1.5-kb XbaI-SacII fragment containing the upstream region of the Trichoderma reesei cellobiohydrolase I gene ( cbh1 ) has been sequenced. The 1.5-kb fragment contains eight 6-bp sites having an identical or similar sequence to the consensus sequence for binding a catabolite repressor, Aspergillus nidulans CreA. Results of binding assays with the maltose-binding protein: :Cre1(10–131) fusion protein (Cre1 is a catabolite repressor of T. reesei ) and the cbhI upstream region revealed that a 504-bp XbaI-NspV fragment (nucleotide position − 1496 to − 993) bearing three 6-bp sites, Al, A2, and A3, and a 356-bp NspV-MunI fragment (nucleotide position −994 to −639) bearing three 6-bp sites, B1, B2, and B3, were shifted in the electrophoretic mobility shift assay. DNase I footprinting experiments showed that the 6-bp sites A2, B1, B2, and B3 were protected from DNase I digestion.     

β-六六六对多刺裸腹溞生命表统计学参数的影响

应用生命表统计学方法研究了不同浓度(0.001、0.01、0.1、1、10、100和1000μg/L)的β-六六六对多刺裸腹溞(Moina macrocopa)种群统计学参数的影响。结果表明,与对照组相比,浓度为1000μg/L的β-六六六显著降低了多刺裸腹溞出生时的生命期望和净生殖率,100和1000μg/L的β-六六六显著降低了多刺裸腹溞的世代时间,0.1和1μg/L的β-六六六显著提高了多刺裸腹溞的种群内禀增长率。     

Molecular cloning of a tumor-associated antigen recognized by monoclonal antibody 3H11

Monoclonal antibody (MAb) 3H11 can bind specifically to different cancer cells from different tissues. MAb 3H11 labeled with radioactive isotopes has been used clinically to detect primary cancer and metastatic cancer. Molecular cloning of the antigen recognized by MAb 3H11 is important in studying tumor occurrence and in developing new biotherapy for cancer. Using MAb 3H11, we screened cDNA library made from the human gastric cancer cell line MGC 803, which reacts with MAb 3H11, and isolated one positive clone specifically recognized by the antibody. The insert cDNA fragment was 0.5 kb. After recombining with glutathione-S-transferase expression vector pGEX-4T, the cDNA fragment could be expressed into a fusion protein that specifically reacted with MAb 3H11. Moreover, the fusion protein could competitively inhibit MAb 3H11 binding to MGC 803 cells. Based on the nucleotide sequence of the cDNA fragment, the full length of the cDNA (2156 bp) was obtained by Rapid-Amplification-cDNA-End (RACE) and nested PCR. Its reading frame was 1767 bp encoding a protein of 589 amino acids. Sequence analysis indicated that there is no highly homologous gene in the GenBank. Northern blot and RT-PCR showed that the mRNA of MAb 3H11 antigen was extensively distributed in embryonic tissue and in different cancerous tissues, but not in corresponding normal tissues. Moreover, in producing antibodies to the antigen expressed prokaryotically, we found that the immunogenicity of the antigen was low in mammalian. Thus we believe that this novel antigen acts as an expression regulator in embryo cells and regains expression in tumor cells. In addition, this antigen is characterized by low differentiation and high proliferation. Molecular function of the antigen needs to be investigated.     

Keratinocyte growth factor: effects on keratinocytes and mechanisms of action

Keratinocyte growth factor (KGF) is a potent and specific mitogen for different types of epithelial cells, and it can protect these cells from various insults. Due to these properties, it is of particular importance for the repair of injured epithelial tissues, and it is currently therapeutically explored for the treatment of radiation- and chemotherapy-induced mucosal epithelial damage in cancer patients. In this review we summarize the current knowledge on the role of KGF in tissue repair and cytoprotection, and we report on its mechanisms of action in keratinocytes.     

Broad substrate specificity of human cytochrome P450 46A1 which initiates cholesterol degradation in the brain

The known activity of cytochrome P450 46A1 (P450 46A1) is 24(S)-hydroxylation of cholesterol. This reaction produces biologically active oxysterol, 24(S)-hydroxycholesterol, and is also the first step in enzymatic degradation of cholesterol in the brain. We report here that P450 46A1 can further metabolize 24(S)-hydroxycholesterol, giving 24,25- and 24,27-dihydroxycholesterols in both the cell cultures transfected with P450 46A1 cDNA and the in vitro reconstituted system with recombinant enzyme. In addition, P450 46A1 was able to carry out side chain hydroxylations of two endogenous C27-steroids with and without a double bond between C5-C6 (7alpha-hydroxycholesterol and cholestanol, respectively) and introduce a hydroxyl group on the steroid nucleus of the C21-steroid hormones with the C4-C5 double bond (progesterone and testosterone). Also, P450 46A1 was found to metabolize xenobiotics carrying out dextromethorphan O- and N-demethylations, diclofenac 4'-hydroxylation, and phenacetin O-deethylation. Thus, substrate specificities of P450 46A1 are not limited to cholesterol and include a number of structurally diverse compounds. Activities of P450 46A1 suggest that, in addition to the involvement in cholesterol homeostasis in the brain, this enzyme may participate in metabolism of neurosteroids and drugs that can cross the blood-brain barrier and are targeted to the central nervous system.     

Comparison of the enzymatic properties of mouse beta-galactoside alpha2,6-sialyltransferases,ST6Gal I and II

The cDNA encoding a second type of mouse beta-galactoside alpha2,6-sialyltransferase (ST6Gal II) was cloned and characterized. The sequence of mouse ST6Gal II encoded a protein of 524 amino acids and showed 77.1% amino acid sequence identity with human ST6Gal II. Recombinant ST6Gal II exhibited alpha2,6-sialyltransferase activity toward oligosaccharides that have the Galbeta1,4GlcNAc sequence at the nonreducing end of their carbohydrate groups, but it exhibited relatively low and no activity toward some glycoproteins and glycolipids, respectively. On the other hand, ST6Gal I, which has been known as the sole member of the ST6Gal-family for more than ten years, exhibited broad substrate specificity toward oligosaccharides, glycoproteins, and a glycolipid, paragloboside. The ST6Gal II gene was mainly expressed in brain and embryo, whereas the ST6Gal I gene was ubiquitously expressed, and its expression levels were higher than those of the ST6Gal II gene. The ST6Gal II gene is located on chromosome 17 and spans over 70 kb of mouse genomic DNA consisting of at least 6 exons. The ST6Gal II gene has a similar genomic structure to the ST6Gal I gene. In this paper, we have shown that ST6Gal II is a counterpart of ST6Gal I.     

Inhibition of epithelial ductal branching in the prostate by sonic hedgehog is indirectly mediated by stromal cells

Sonic hedgehog (Shh), a vertebrate homologue of the Drosophila segment-polarity gene hedgehog, has been reported to play an important role during normal development of various tissues. Abnormal activities of Shh signaling pathway have been implicated in tumorigenesis such as basal cell carcinomas and medulloblastomas. Here we show that Shh signaling negatively regulates prostatic epithelial ductal morphogenesis. In organotypic cultures of developing rat prostates, Shh inhibited cell proliferation and promoted differentiation of luminal epithelial cells. The expression pattern of Shh and its receptors suggests a paracrine mechanism of action. The Shh receptors Ptc1 (Patched1) and Ptc2 were found to be expressed in prostatic stromal cells adjacent to the epithelium, where Shh itself was produced. This paracrine model was confirmed by co-culturing the developing prostate in the presence of stromal cells transfected with a vector expressing a constitutively active form of Smoothened, the real effector of the Shh signaling pathway. Furthermore, expression of activin A and TGF-beta1 that were shown previously to inhibit prostatic epithelial branching was up-regulated following Shh treatment in the organotypic cultures. Taken together, these results suggest that Shh negatively regulates prostatic ductal branching indirectly by acting on the surrounding stromal cells, at least partly via up-regulating expression of activin A and TGF-beta1.