Identification of AHBA Biosynthetic Genes Related to Geldanamycin Biosynthesis in Streptomyces hygroscopicus 17997

To clone and study the geldanamycin biosynthetic gene cluster in Streptomyces hygroscopicus 17997, we designed degenerate primers based on the conserved sequence of the ansamycin 3-amino-5-hydroxybenzoic acid (AHBA) synthase gene. A 755-bp polymerase chain reaction product was obtained from S. hygroscopicus 17997 genomic DNA, which showed high similarity to ansamycin AHBA synthase genes. Through screening the cosmid library of S. hygroscopicus 17997, two loci of separated AHBA biosynthetic gene clusters were discovered. Comparisons of sequence homology and gene organization indicated that the two AHBA biosynthetic gene clusters could be divided into a benzenic and a naphthalenic subgroup. Gene disruption demonstrated that the benzenic AHBA gene cluster is involved in the biosynthesis of geldanamycin. However, the naphthalenic AHBA genes in the genome of Streptomyces hygroscopicus 17997 could not complement the deficiency of the benzenic AHBA genes. This is the first report on the AHBA biosynthetic gene cluster in a geldanamycin-producing strain. W. He and L. Wu contributed equally to this work.     

The effect of tripeptide tyroserleutide (YSL) on animal models of hepatocarcinoma

This study aimed to observe the effects of tyroserleutide (tyrosyl-seryl-leucine, YSL) on the survival time of mice transplanted with the ascitic fluid-type hepatocarcinoma H22, as well as the inhibitory effect of tyroserleutide on the human hepatocarcinoma Bel-7402 that was transplanted into nude mice. At doses of 80, 20 and 5 microg/kg/d, tyroserleutide significantly prolonged the survival of mice transplanted with H22 tumor cells, producing survival rates of 89%, 39% and 49%, respectively, which were statistically significantly different from the saline group (P < 0.05). YSL, at doses of 80, 160 and 320 microg/kg/d significantly inhibited the growth of the human hepatocarcinoma Bel-7402 tumor in nude mice, producing inhibition of 40%, 64% and 59%, respectively; this inhibition was significantly greater than that by saline (P < 0.05). HE staining and electron microscopy of the pathological changes of the tumor in nude mice showed that YSL changed the structure Bel-7402 tumor cells that were transplanted into nude mice, and also induced tumor cell apoptosis and necrosis, which could be a mechanism by which YSL inhibits the tumor growth in animal models.     

Differences in hypothyroidism between lithium-free and -treated patients with bipolar disorders

The majority of the previous studies of thyroid abnormalities in bipolar patients was conducted in populations containing various proportions of lithium-treated subjects. In the present study, we sought to determine whether there exist differences in hypothyroid profile between lithium-free and -treated bipolar patients. Bipolar patients never treated with lithium and carbamazepine (n=78) and those currently in lithium therapy (n=53) were included in this study. Serum concentrations of total thyroxine (T(4)), total triiodothyronine (T(3)), and thyroid-stimulating hormone (TSH) were compared between lithium-free and -treated patients. The rate of hypothyroidism in lithium-free patients was significantly lower than those treated with lithium (6.3%-10.8% vs. 28.0%-32.1%). Significant changes in the three thyroid indices indicative of hypothyroidism were consistently associated with longer illness duration in lithium-free manic patients, but with greater severity of mania and more mood episodes in their lithium-treated counterparts. In lithium-free depressed patients, more episodes were associated with lower T(4) levels; whereas in their lithium-treated counterparts, longer illness duration was associated with higher TSH levels and females with lower T(3) levels. These results suggest that bipolar patients with and without lithium exposure differ in prevalence and association of hypothyroidism and may have different response to thyroid hormone therapy.     

Serum LncRNAs Profiles Serve as Novel Potential Biomarkers for the Diagnosis of HBV-Positive Hepatocellular Carcinoma

Background

Hepatocellular carcinoma (HCC) is a common malignancy that has a poor prognosis because there is lack of methods for early diagnosis. We aimed to utilize two serum long non-coding RNAs (lncRNAs), uc001ncr and {"type":"entrez-nucleotide","attrs":{"text":"AX800134","term_id":"37653391"}}AX800134, to diagnose hepatitis B virus (HBV)–positive HCC.

Methods

lncRNA microarrays were utilized to measure the differential expression of lncRNAs between tumor tissues and corresponding non-tumor tissues in HBV-positive hapatocellular carcinoma. uc001ncr and {"type":"entrez-nucleotide","attrs":{"text":"AX800134","term_id":"37653391"}}AX800134 were selected as candidate lncRNAs and detected in three independent cohorts containing a total of 684 participants (healthy individuals and chronic HBV patients and HBV-positive HCC patients) who were recruited between March 2011 and December 2012. A logistic regression model was constructed using a training cohort (n = 353) and validated using an independent cohort (n = 181). The area under the receiver operating characteristic curve (AUC) was utilized to evaluate the diagnostic accuracy.

Results

We determined that a panel based on the expression of uc001ncr and {"type":"entrez-nucleotide","attrs":{"text":"AX800134","term_id":"37653391"}}AX800134 accurately diagnosed HBV-positive HCC (AUC values of 0.9494 and 0.9491 for the training and validation cohorts, respectively). The diagnostic performance of the panel remained high in patients with AFP≤400 ng/ml (AUC values of 0.9371 and 0.9527 for the training and validation cohorts, respectively). The panel also diagnosed early HCC (AUC values of 0.9450 and 0.9564 for the training and validation cohorts, respectively).

Conclusion

Our results indicated that the serum expression of uc001ncr and {"type":"entrez-nucleotide","attrs":{"text":"AX800134","term_id":"37653391"}}AX800134 has potential as novel potential biomarker for the diagnosis of HCC, especially in patients with AFP≤400 ng/ml or early-stage disease (BCLC 0+A).     

kpsE和kpsD双基因缺失显著降低肠道外致病性大肠杆菌的毒力

【目的】探究荚膜对肠道外致病性大肠杆菌致病作用的影响。【方法】选取负责荚膜多糖转运的基因kpsE和kpsD,利用λRed重组系统构建APEC E058和UPEC U17荚膜缺失株E058ΔkpsED和U17ΔkpsED,并通过一系列的体内及体外试验对其生物学特性及致病性进行研究。【结果】双基因缺失株的生长速度较野生株没有明显差异,但缺失株抗血清补体杀菌能力和抗鸡巨噬细胞HD-11细胞吞噬能力显著下降。1日龄雏鸡LD50致病性试验结果显示,缺失株E058ΔkpsED和U17ΔkpsED对鸡失去致病力,而回复株毒力恢复至野生株水平;35日龄SPF鸡体内动态分布和竞争试验显示ΔkpsED缺失株在鸡体内定殖能力和竞争性生长能力显著下降,表明kpsED双基因的缺失能显著降低APEC E058和UPEC U17的致病力。【结论】荚膜与肠道外致病性大肠杆菌的致病性相关,是其重要的毒力因子。     

基因组磷硫酰化修饰的研究进展及展望北大核心CSCD

DNA磷硫酰化修饰是DNA骨架上的第一例生理修饰。该修饰由dnd ABCDE编码的5个蛋白协同作用,以硫原子取代DNA磷酸二酯键上一个非桥接的氧原子。研究发现,DNA磷硫酰化修饰广泛存在于各种微生物中,在不同细菌中存在序列特异性,且具有R_P空间构象专一性。近年来,对DNA磷硫酰化修饰的研究取得了一系列的成果。为了对DNA磷硫酰化修饰有一个系统全面的了解,本文将就这一特殊生理修饰的发现过程,研究进展,未来所面临的机遇及挑战作一个简要的概述。     

A Two-Stage Adaptive Targeted Clinical Trial Design for Biomarker Performance-Based Sample Size Re-Estimation

Biomarker-directed targeted clinical trial is aimed at developing pharmaceutical agents for a targeted patient subpopulation sharing a specific disease etiology. Biomarker plays a key role in patient enrichment for targeted trials. Biomarker performance substantially impacts heterogeneity of a targeted study population and consequently trial efficiency, statistical power, information accumulation, and early stopping decision-making (Simon and Maitournam in Clinical Cancer Res 10:6759-6763, 2004; Maitournam and Simon in Stat Med 24:329-339, 2005; Gao et al. in Contemp Clin Trials 42:119-131, 2015). Hence, accurate assessment of biomarker performance is crucial to sample size calculation in planning of targeted trials. However, prior knowledge of biomarker performance is often limited at the planning stage due to inadequacy of biomarker validation, differences between study populations in demographic characteristics and trial settings, etc. Under this circumstance, adaptive design would be useful in updating biomarker performance and re-estimating sample sizes when a targeted trial is ongoing. In this paper, we propose a two-stage adaptive design that provides flexibility in biomarker performance-based sample size adaption for targeted trials. The design can facilitate a targeted trial to achieve planned statistical power by re-assessment of actual biomarker performance and subsequent sample size adaption while preserving desired type-1 error.     

A new paradigm of DNA synthesis: three-metal-ion catalysis

Enzyme catalysis has been studied for over a century. How it actually occurs has not been visualized until recently. By combining in crystallo reaction and X-ray diffraction analysis of reaction intermediates, we have obtained unprecedented atomic details of the DNA synthesis process. Contrary to the established theory that enzyme-substrate complexes and transition states have identical atomic composition and catalysis occurs by the two-metal-ion mechanism, we have discovered that an additional divalent cation has to be captured en route to product formation. Unlike the canonical two metal ions, which are coordinated by DNA polymerases, this third metal ion is free of enzyme coordination. Its location between the α- and β-phosphates of dNTP suggests that the third metal ion may drive the phosphoryltransfer from the leaving group opposite to the 3′-OH nucleophile. Experimental data indicate that binding of the third metal ion may be the rate-limiting step in DNA synthesis and the free energy associated with the metal-ion binding can overcome the activation barrier to the DNA synthesis reaction.     

MAP4K4: an emerging therapeutic target in cancer

The serine/threonine kinase MAP4K4 is a member of the Ste20p (sterile 20 protein) family. MAP4K4 was initially discovered in 1995 as a key kinase in the mating pathway in Saccharomyces cerevisiae and was later found to be involved in many aspects of cell functions and many biological and pathological processes. The role of MAP4K4 in immunity, inflammation, metabolic and cardiovascular disease has been recognized. Information regarding MAP4K4 in cancers is extremely limited, but increasing evidence suggests that MAP4K4 also plays an important role in cancer and MAP4K4 may represent a novel actionable cancer therapeutic target. This review summarizes our current understanding of MAP4K4 regulation and MAP4K4 in cancer. MAP4K4-specific inhibitors have been recently developed. We hope that this review article would advocate more basic and preclinical research on MAP4K4 in cancer, which could ultimately provide biological and mechanistic justifications for preclinical and clinical test of MAP4K4 inhibitor in cancer patients.