Methylation protects miRNAs and siRNAs from a 3'-end uridylation activity in Arabidopsis

Small RNAs of 21-25 nucleotides (nt), including small interfering RNAs (siRNAs) and microRNAs (miRNAs), act as guide RNAs to silence target-gene expression in a sequence-specific manner. In addition to a Dicer homolog, DCL1, the biogenesis of miRNAs in Arabidopsis requires another protein, HEN1. miRNAs are reduced in abundance and increased in size in hen1 mutants. We found that HEN1 is a miRNA methyltransferase that adds a methyl group to the 3'-most nucleotide of miRNAs, but the role of miRNA methylation was unknown. Here, we show that siRNAs from sense transgenes, hairpin transgenes, and transposons or repeat sequences, as well as a new class of siRNAs known as trans-acting siRNAs, are also methylated in vivo by HEN1. In addition, we show that the size increase of small RNAs in the hen1-1 mutant is due to the addition of one to five U residues to the 3' ends of the small RNAs. Therefore, a novel uridylation activity targets the 3' ends of unmethylated miRNAs and siRNAs in hen1 mutants. We conclude that 3'-end methylation is a common step in miRNA and siRNA metabolism and likely protects the 3' ends of the small RNAs from the uridylation activity.     

Generation and Analysis of ESTs from the Grass Carp,Ctenopharyngodon idellus

Grass carp, Ctenopharyngodon idellus (Valenciennes, 1844), is an economically important species widely cultured in the world, but its genome research resources are largely lacking. The objectives of this study were to construct normalized cDNA libraries for efficient EST analysis, to generate ESTs from these libraries, and to identify EST-related molecular markers such as microsatellites and single nucleotide polymorphisms (SNPs) for genetic analysis of this species. A total of 6,269 ESTs were generated representing 4,815 unique sequences, from which 105 putative microsatellites and 5,228 SNPs were identified. These genome resources provide the material basis for future genetic and functional analyses in this species.     

Comparative cardiac mechanics: Laplace's Law

The pumping ability of the heart is determined by mechanical and geometrical factors. These latter are governed by Laplace's Law. The extent of the applicability of this law across mammalian species is examined utilizing allometric relations and dimensional analysis. Results show that Laplace's Law plays an important role in linking the anatomical design to the functional capability of mammalian hearts.     

PNAS-4 expression and its relationship to p53 in colorectal cancer

PNAS-4 is a novel pro-apoptotic protein activated during the early response to DNA damage; however, the molecular mechanisms and pathways regulating PNAS-4 expression in tumors are not well understood. We hypothesized that PNAS-4 is a p53 down-stream target gene and designed this study. We searched online for putative p53-binding sites in the entire PNAS-4 gene and did not find any corresponding information. In HCT116 colon cancer cells, after being transfected with small interfering RNA to silence p53, the expressions of PNAS-4 and other known p53 target gene (Apaf1, Bax, Fas and Dr5) were determined by real-time PCR. We found that PNAS-4 was up-regulated while Apaf1, Bax, Fas and Dr5 were down-regulated. We then examined the expression of PNAS-4 and p53 mutation in colorectal cancer patients. PNAS-4 expressed both in colorectal cancers and normal tissues, but compared with paired control, PNAS-4 was up-regulated in cancers (P = 0.018). PNAS-4 overexpression ratios were correlated to the p53 mutant status (P = 0.001). The mean PNAS-4 expression levels of p53 mutant homozygote group and heterozygote group were higher than that of p53 wild type group (P = 0.013). The expression ratios of PNAS-4 (every sample in relative to its paired normal mucosa) were different between negative lymph node metastasis (66% up-regulated, 34% down-regulated) and positive metastasis (42% up-regulated, 58% down-regulated). Taken together, these findings suggested that PNAS-4 was not a p53 target, but overexpression of PNAS-4 was correlated to p53 inactivity in colorectal cancer.     

嘌呤拟似物对豚鼠胃窦环行肌自发性收缩及电活动的影响

为探讨非肾上腺素能非胆碱能神经递质对胃窦环行肌功能的调节作用,在离体胃平滑肌上观察了嘌呤拟似物对胃窦环行肌自发性收缩活动和电活动的影响。电活动用传统的细胞内微电极记录,并和收缩活动同步描记于多道生理记录仪。结果表明,嘌呤能P2Y受体激动剂,三磷酸腺苷(ATP)和2-methylthio ATP(2-MeSATP)均增强胃窦平滑肌的收缩活动,但不影响电活动,而且ATP和2-MeSATP对胃平滑肌收缩活动的增强作用可被嘌呤能P2Y受体阻断剂,reactive blue-2和苏拉明(suramin)所阻断。用100μmol／L α,β-MeATP引起的脱敏感使P2X受体被阻断,ATP增强胃窦平滑肌收缩活动的效应不受影响。嘌呤能P2X受体激动剂,α,β-MeATP明显抑制胃窦环行肌自发性收缩活动,同时使膜电位明显超极化。ATP对胃窦平滑肌的收缩作用不被L型钙通道阻断剂尼卡地平(nicardipine)阻断,但细胞外用无钙液灌流时这种效应则完全被阻断。用前列腺素合成抑制剂消炎痛预先处理20min后,ATP和2-MeSATP仍能增强胃窦平滑肌的自发性收缩活动。以上结果提示：(1)ATP和2-MeSATP通过嘌呤能P2Y受体增强胃窦平滑肌的自发性收缩活动,而α,β-MeATP或β,γ-MeATP通过嘌呤能P2X受体使膜电位超极化,引起胃窦平滑肌的舒张;(2)ATP和2-MeSATP增强胃窦平滑肌自发性收缩活动的效应依赖于细胞外钙,但钙离子进入细胞的途径并不是电压依赖性钙通道;(3)ATP和2-MeSATP增强胃窦平滑肌自发性收缩活动的效应不通过前列腺素介导。     

Pattern recognition analysis to the variation of nasal-pharynx cancer patients' trace element levels in samples of hair,whole blood,and tissue

Pattern recognition has been used in this paper to analyze trace element levels in patients diagnosed with nasal-pharynx cancer (NPC) and in healthy control subjects. Trace elements such as Zn, Cu, Fe, Mn, and Mg have been tested in samples of hair and whole blood. Through Mahalanobis Distance Decision analysis, we have achieved good classification effects in whole blood samples: Efficiency for distinguishing patients is 96% and that of healthy controls is 90%. Classification hair samples is inferior to whole blood: Decision accuracy for patients is 58% and healthy controls is 90%. These results are also shown in a nonlinear mapping figure. At the same time, we have also determined 5 trace element levels in 16 other cancer patients' nonneoplastic and cancerous tissue, with no significant difference between them: Decision accuracy of cancerous tissue is 63%, and in nonneoplastic tissue is 50%, hence, we cannot identify them. It can be inferred that there is no idiosyncratic change of trace elements in cancer patients' neoplastic tissue, the change of a cancerous person may occur in the whole body.