表没食子儿茶素没食子酸酯对人结肠癌HT-29细胞G1期的阻滞作用

目的:研究表没食子儿茶素没食子酸酯(Epigallaocatechin-3-gallate,EGCG)时人结肠癌HT-29细胞增殖的影响.方法:实验分为EGCG不同浓度处理组和阴性对照组.采用MTT比色法检测EGCG(30μg/mL、40μg/mL、50μg/mL、60μg/mL、70μg/mL)对HT-29细胞的生长影响;应用流式细胞术分析EGCG对HT-29细胞周期分布的影响;免疫印迹观测EGCG对HT-29细胞p38MAPK、cyclinD1蛋白表达的影响.结果:MTT比色结果显示.不同浓度EGCG(30μg/ml、40μg/ml、50μg/ml、60μg/ml)对HT-29细胞具有明显的生长抑制作用,并呈剂量-效应依赖关系(P<0.05);流式细胞术分析显示,EGCG诱导人结肠癌细胞G1期阻滞,且随着处理时间的延长,其诱导周期阻滞的效应越明显(P<0.05);蛋白免疫印迹显示.总的p38MAPK不随处理时间和浓度的改变而改变,但是磷酸化的p38MAPK蛋白的表达随处理时间和处理浓度的增加而明显增加,而CyclinD1蛋白的表达随处理浓度的增加而明显减少.结论:EGCG诱导HT-29细胞G1期阻滞,抑制细胞增殖,可能与活化p38MAPK,下调CyclinD1蛋白表达有关.     

Molecular evolution of olfactomedin

Olfactomedin is a secreted polymeric glycoprotein of unknown function, originally discovered at the mucociliary surface of the amphibian olfactory neuroepithelium and subsequently found throughout the mammalian brain. As a first step toward elucidating the function of olfactomedin, its phylogenetic history was examined to identify conserved structural motifs. Such conserved motifs may have functional significance and provide targets for future mutagenesis studies aimed at establishing the function of this protein. Previous studies revealed 33% amino acid sequence identity between rat and frog olfactomedins in their carboxyl terminal segments. Further analysis, however, reveals more extensive homologies throughout the molecule. Despite significant sequence divergence, cysteines essential for homopolymer formation such as the CXC motif near the amino terminus are conserved, as is the characteristic glycosylation pattern, suggesting that these posttranslational modifications are essential for function. Furthermore, evolutionary analysis of a region of 53 amino acids of fish, frog, rat, mouse, and human olfactomedins indicates that an ancestral olfactomedin gene arose before the evolution of terrestrial vertebrates and evolved independently in teleost, amphibian, and mammalian lineages. Indeed, a distant olfactomedin homolog was identified in Caenorhabditis elegans. Although the amino acid sequence of this invertebrate protein is longer and highly divergent compared with its vertebrate homologs, the protein from C. elegans shows remarkable similarities in terms of conserved motifs and posttranslational modification sites. Six universally conserved motifs were identified, and five of these are clustered in the carboxyl terminal half of the protein. Sequence comparisons indicate that evolution of the N-terminal half of the molecule involved extensive insertions and deletions; the C-terminal segment evolved mostly through point mutations, at least during vertebrate evolution. The widespread occurrence of olfactomedin among vertebrates and invertebrates underscores the notion that this protein has a function of universal importance. Furthermore, extensive modification of its N-terminal half and the acquisition of a C-terminal SDEL endoplasmic-reticulum- targeting sequence may have enabled olfactomedin to adopt new functions in the mammalian central nervous system.      

The molecular organization of the beta-globin complex of the deer mouse, Peromyscus maniculatus

Recombinant DNA clones have been isolated that contain 80 kb of the beta-globin complex from the deer mouse, Peromyscus maniculatus. Comparisons of this complex with that from the laboratory mouse, Mus domesticus (with an order 5'-Hbby, Hbb-bhO, Hbb-bhl, Hbb-bh2, Hbb-bh3, Hbb-bl, Hbb-b2 3') highlight organizational trends in the beta-globin complex since the two species diverged. Unlike other mammals studied thus far, the deer mouse possesses three adult genes. Partial sequence analysis indicates that each of the three adult genes is intact and hence may be functional. Hybridization of one of the two Mus pseudogenes, Hbb-bh3, to genomic blots from Peromyscus reveals that it has a homologous counterpart in Peromyscus. Homologous genes to the two gamma-like Mus genes, Hbb-bhO and Hbb-bhl, are also found in Peromyscus. The strong hybridization between the Hbb-bhl genes and significant nucleotide similarity between the Hbb-bhO genes suggest that both pairs are important for the ontogeny of these mice although no known product has been identified for the Hbb-bhO genes. The presence of Hbb-bhO and Hbb-bhl in Peromyscus suggests that the duplication that created this related gene set occurred before the two lineages diverged. A single gene for Hbb-y has been isolated from Peromyscus. The adult region in Peromyscus has undergone significant divergence from the same region in Mus, having three rather than two adult genes, the acquisition of at least 15 kb of extra DNA relative to Mus, and possibly the loss of the Hbb-bh2 pseudogene. The nonadult region of the complex, in contrast, contains the same set of genes apparently distributed over the same amount of DNA as in the Mus beta- globin complex. This observation suggests that the embryonic region of the complex is more evolutionarily stable than the adult region.