Isolation and characterization of two Medicago falcate AP2/EREBP family transcription factor cDNA, MfDREB1 and MfDREB1s.

DREB transcription factors play an important role in tolerance to abiotic stress in high plants. In this work, two new DRE-binding protein genes MfDREB1 and MfDREB1s cDNA that encoded an AP2/EREBP type transcription factor were isolated by RT-PCR from Medicago falcate seedlings. Sequence analysis showed MfDREB1 and MfDREB1s were almost identical except that there was a 202bp fragment at the 3' end of the MfDREB1s cDNA that is absent in MfDREB1 cDNA. The MfDREB1 has a open reading frame of 651bp, which encodes 216 amino acid residues. The putative protein is deduced a predicted molecular mass of 24.6kDa and a pI of 5.95. The MfDREB1s has a open reading frame of 555bp, the putative protein is 184 amino acid long with a predicted molecular weight of 20.8kDa, pI 9.11. The Protein Blast data revealed that the two proteins can be classified as a typical member of the AP2/EREBP family of DNA-binding proteins. The comparison of the MfDREB1 cDNA and MfDREB1s cDNA with their corresponding genes in genomic DNA showed that the size and nucleotide sequence of the cDNA was identical to that of the genomic DNA. This suggested that the genomic MfDREB1 gene and MfDREB1s gene had no introns. Southern blot analysis indicated that MfDREB1 and MfDREB1s are multi-copy genes in Medicago falcate genome. Northern blot analysis indicated that the MfDREB1 and MfDREB1s genes were induced by low temperature stress.

Construction and analysis of high-complexity ribosome display random peptide libraries.

Random peptide libraries displayed on the ribosome are becoming a new tool for the in vitro selection of biologically relevant macromolecules, including epitopes, antagonists, enzymes, and cell-surface receptors. Ribosome display is a cell-free system of coupling individual nascent proteins (phenotypes) to their corresponding mRNA (genotypes) by the formation of stable protein-ribosome-mRNA complexes and permitting the selection of a functional nascent protein by iterative cycles of panning and reverse transcription-polymerase chain reaction (RT-PCR) amplification in vitro. The complexity of the random peptide library is critical for the success of a panning experiment; greater the diversity of sequences within the library, the more likely it is that the library comprises sequences that can bind a given target with specific affinity. Here, we have used the cell-free system Escherichia coli S30 lysate to construct high-complexity random peptide libraries (>10(14) independent members) by introducing strategies that are different from the methods described by Mattheakis et al. and Lamla et al. The key step in our method is to produce nanomole (nmol) amounts of DNA elements that are necessary for in vitro transcription/translation by using PCR but not plasmid DNA. Library design strategies and protocols that facilitate rapid identification are also presented.

High-level expression of functional tumor suppressor LKB1 in Escherichia coli.

The human LKB1 tumor suppressor has been implicated as an important regulator of many cellular processes and signaling pathways, indicating that it could be a good candidate for anticancer drugs. The failure of its obtain high-level expression has been a major obstacle to study its protein structure and function in vitro. Here, we describe the high-level expression of human LKB1 in Escherichia coli and show its kinase activity and anticancer effects on a tumor cell line. The gene encoding LKB1 was optimized by replacing rare codons with codons frequently used in E. coli and synthesized with overlapping primers. The recombinant His-LKB1 was expressed in hosts BL21(DE3) (BL) and Rosetta-gami(DE3)pLysS (RG). His-LKB1 from BL was present mainly as inclusion body. The soluble His-LKB1 from RG accounted for 34.1% of total proteins and the yield of purified His-LKB1 was approximately 92 microg/ml. Purified His-LKB1 protein from both hosts was functionally active, as shown by reversible autophosphorylation and kinase activity in the absence of any other associated kinase. The growth inhibitory ratio of the purified BL-derived and RG-derived His-LKB1 on hepatic carcinoma SMMC-7721 cells was 24.97% and 45.68%, respectively, and both could produce significant cell-cycle arrest.

[Expression of functional human STK11 protein in Escherichia coli].

STK11 (serine/threonine kinase 11 ), a multi-functional protein reported recently, possibly participates in a broad range of cellular processes, including regulation of cell cycle, p53-mediated apoptosis, ras-induced cell transformation and cell polarization. An efficient expression of functional STK11 in Escherichia coli will promote the study on its structure and function. Inducible prokaryotic expression vector pET-Nus-STK11 (with Nus fusion tag) was constructed with pET-44a( + ) and the cDNA of STK11 gene cloned in our lab. pET-Nus-STK11 was then expressed in both BL21 (DE3) and Rosetta-gami (DE3)pLysS on the induction of IPTG. SDS-PAGE and Western blot indicated that recombinant Nus-STK11 obtained in BL21(DE3) was in the form of inclusion body, whereas that from Rosetta-gami (DE3)pLysS was mainly in soluble fraction, and accounted for 8.9% and 16.7% of the total protein, respectively. After purification and refolding, the obtained recombinant protein was carried into SMMC-7721 cells by Chariot to observe its influence on cell growth and cell cycle. Nus-STK 1 from BL21(DE3) was proved to be lack of any tumor-suppression activity, while a growth inhibitory ratio of 47.05% on SMMC-7721 cell was observed, and cell cycle progression of SMMC-7721 cells was also arrested from G0/G1 to S phase, with the Nus-STK11 from Rosetta-gami (DE3) pLysS, indicating that the above recombinant fusion protein from Rosetta-gami (DE3)pLysS had significant biological activity. This is the first report on functional recombinant STK11 protein expressed in Escherichia coli.

[Polymorphism of CYP1A1 gene Msp I site in the Mongolian and Han nationality populations of Inner Mongolia of China].

OBJECTIVE: To study the polymorphism of CYP1A1 gene Msp I site in the Mongolian and Han nationality populations of Inner Mongolia. METHODS: The PCR-restriction fragment length polymorphism(PCR-RFLP) technique was used to analyze the genotypes of CYP1A1 gene Msp I site in 80 subjects of Mongolian nationality and 120 subjects of Han nationality among whom there is no blood relationship each other. RESULTS: The genotype frequency of CYP1A1 gene Msp I site showed that the wild-type, heterozygote, homozygous variants were 35.0%, 48.7%, 16.3% and 33.3%, 52.5%, 14.2% respectively distributions of Mongolian nationality and Han nationality population, and the Chi-square tests showed that there was no significant difference between the two groups. CONCLUSION: The genotype frequency distributions of CYP1A1 gene Msp I site did not exhibit the obvious difference between Mongolian nationality and Han nationality population of Inner Mongolia.

[Influence of smoke tar on mRNA expression of aromatic hydrocarbon receptor and cytochrome P4501A1 gene of mice lungs].

OBJECTIVE: To investigate the influence of the smoke tar on the expression of aromatic hydrocarbon receptor (AHR) and the cytochrome P4501Al (CYP1A1) gene of mice lungs. METHODS: The smoke tar of 5.29, 10.58 and 15.87 mg/kg was administered intraperitoneally in mice respectively. RNA of mice lungs was got with RNA kit. RT-PCR technique was used for determining AHR and CYP1A1 gene expression with beta-actin as control. RESULTS: The AHR gene expression level was (0.554 +/- 0.023) for the mice intraperitoneally administered with 5.29 mg/kg smoke tar for 72 hours with the significant difference in gene expression level compared with the Tween-80 group (0.484 +/- 0.045) (P < 0.05). The AHR gene expression levels were (0.555 +/- 0.014), (0.606 +/- 0.051), and (0.566 +/- 0.014), (0.684 +/- 0.069) for the mice intraperitoneally administered with 10.58 and 15.87 mg/kg smoke tar for 48 hours and 72 hours respectively with the significant difference in gene expression level compared with the Tween-80 group (0.486 +/- 0.060, 0.484 +/- 0.045) (P < 0.05, P < 0.01). The CYP1Al gene expression levels were (1.535 +/- 0.021), (1.643 +/- 0.046) and (1.624 +/- 0.056), (1.739 +/- 0.038) respectively with the significant difference compared with the Tween-80 group (l.436 +/- 0.016, 1.404 +/- 0.036) (P < 0.01). CONCLUSION: The smoke tar can regulate up the expression of AHR and CYP1A1 gene at a certain dosage and time. The regulation of the smoke tar for the expression of AHR was earlier than for that of CYP1A1.

[Prokaryotic expression of functional PTEN in Escherichia coli and preparation of polyclonal antibody].

PTEN, a dual-specificity phosphatase, exerts its tumor-suppressive effects through the inhibition of cell cycle progression and cell immigration, therefore could be an important candidate for tumor-suppression. As study on prokaryotic expression of PTEN and its anti-tumor functions has not been reported, the present study aims at an efficient expression of functional PTEN in Escherichia coli and the investigation of its tumor-suppression activity. PTEN cDNA cloned in our lab previously was recombined into prokaryotic expression vector pET-44a(+) to construct pET-PTEN (pEP) and pET-Nus-PTEN (pENP). PTEN was fused with 6 x His tag in pEP, and with Nus in pENP, which could be useful for a stable and soluble expression. The recombinant vectors were transformed into both BL21 (DE3) (BL) and Rosetta-gami (DE3) pLysS (RG). The former is a normal expression host while the latter is optimized for expression of eukaryotic genes and folding of target proteins. On the induction of 0.5mmol/L IPTG, 55kD and 118kD specific protein bands were observed, corresponding to His-PTEN and Nus-PTEN fusion proteins, respectively. Western blot analysis showed the recombinant fusion proteins could react with PTEN polyclonal antibody. The recombinant HTEN was expressed both in soluble fraction and inclusion body. Higher expression levels of recombinant PTEN were obtained in BL (His-PTEN: 10.3%; NusA-PTEN: 18.7%), whereas the higher percentages of soluble recombinant proteins were observed in RG (His-PTEN: 4.7%; Nus-PTEN: 6.6%). The obtained recombinant fusion proteins were purified by affinity chromatography and were showed to be homogeneous in SDS-PAGE. In tumor-suppression experiments, His-PTEN was proved to have significant inhibition on growth of mice solid tumor with an inhibitory ratio of 58.76%, and on the proliferation of DU-145 tumor cells with an inhibitory ratio of 46.16%. The cell cycle progression of DU-145 tumor cells was also arrested from G0/G1 to S phase. His-PTEN from RG was proved to have significantly higher tumor-suppression activity than that from BL, indicating that there may be some advantages for eukaryotic genes to be expressed in the former host. This is the report of functional recombinant PTEN expressed in Escherichia coli. Purified His-PTEN was used for immunizing Kunming mice, and ascitic polyclonal antibodies raised against His-PTEN were generated using sarcoma 180 cells. At 1:2000 dilution, the antibodies could interact with PTEN by western blot. The present study has laid a foundation for application of PTEN in cancer therapy.

[Relationship between CYP1A1 and GSTM1 genetic polymorphisms and lung cancer susceptibility in population of Inner Mongolia].

BACKGROUND: Lung cancer is one of malignant tumors to hurt human health. It has been known that the development of lung cancer may be associated with genetic polymorphism of some lung cancer related genes. The aim of this study is to explore the susceptibility to lung cancer in relation to CYP1A1 and GSTM1 genetic polymorphisms in population of Inner Mongolia. METHODS: CYP1A1 and GSTM1 genetic polymorphisms were determined by PCR-RFLP in 163 lung cancer cases and healthy controls respectively. RESULTS: The frequencies of CYP1A1 variation genotype (vt/vt) and GSTM1(-) were 36.8% and 65.0% in lung cancer cases and 19.0% and 48.9% in healthy controls respectively. Statistical tests showed significant difference in the frequencies between the two groups (Chi-Square =12.82, P=0.0001; Chi-Square = 9.78, P=0.002). The risk of lung cancer with CYP1A1 variation genotype was significantly higher than those of controls (OR= 2.48, 95% CI=1.51-4.08). The individuals who carried with GSTM1-null genotype had a high risk of lung cancer (OR=2.03, 95% CI=1.30-3.17). Combined analysis of the polymorphisms showed that percentage of CYP1A1(vt/vt)/GSTM1(-) in lung cancer and control groups was 28.8% and 8.0% respectively (Chi-Square = 23.883, P=0.0001). The people who carried with CYP1A1(vt/vt)/GSTM1(-) had a high risk of lung cancer (OR=4.90, 95% CI=2.50-9.83). Pearson Chi-Square of sex differential showed there was no significance between the homozygous variation genotype of CYP1A1/GSTM1(-) and the other genotypes of CYP1A1/GSTM1(-) neither in lung cancer group (Chi-Square=0.797, P=0.372) nor in control group (Chi-Square=0.670, P=0.761). Statistical tests showed that susceptibility to lung cancer was related to smoking (Chi-Square = 14.197, P=0.000), the risk of lung cancer in smoking individuals raised remarkably (OR=2.33, 95% CI=1.50-3.62). There may be a synergetic interaction between CYP1A1 variation genotype (vt/vt) and smoking on the elevated susceptibility to lung cancer (Chi-Square = 23.843, P=0.000), the smokers who carried with CYP1A1 (vt/vt) had a significantly higher risk of lung cancer (OR=4.44, 95% CI=2.40-8.32, Chi-Square = 23.843, P= 0.000). So did the GSTM1(-) and smoking on the elevated susceptibility to lung cancer, the significantly higher risk of lung cancer had also been found in those smokers who carried with GSTM1(-) (OR=7.32, 95% CI=3.39-15.50, Chi-Square = 36.708,P=0.000). CONCLUSIONS: The polymorphisms of CYP1A1 vt/vt and GSTM1(-) are the risk factors in lung cancer of Inner Mongolia. Smoking is also related to the susceptibility to lung cancer. There may be a synergetic interaction between CYP1A1 (vt/vt) and GSTM1(-) on the elevated susceptibility of lung cancer. So do the CYP1A1 (vt/vt), GSTM1(-) and smoking.

[HPRT gene knock-out from rat fetal neural stem cells].

The 3.0 kb 5' arm (long arm, LA) of rat HPRT gene knock-out vector was cut by Sal I from rat HPRT gene genomic bacterial artificial chromosome (BAC) , and the 1.7 kb 3' arm (short arm, SA) was proliferated by PCR. Neo', 5' arm, 3' arm were sequentially cloned into pBS vector's relative restriction enzyme sites. For acquirement of tk gene, the 5' arm -Neo' -3' arm fragment inserted into pKO vector to construct pKO-HPRT. The pKO-HPRT was linearized by Not I, extracted by ethidium bromide, butanol and phenol/chloroform, and dialyzed by 0.025 microlmol/L Millipore. At the same time, rat neural stem cells cultured from E14.5-16.5 rat fetal brain. Passage 2 rFNSCs was tranfected by linearized pKO-HPRT with Fugene-6t transfection reagents. After 80 microg/ml G418 and 0.2 micromol/L ganciclovir selection, the survived cells was cultured in suspension to form neural spheres. The spheres can be picked up under the microscopy, and proliferated in 96- ,48- and 24-well plates sequentially. When the cell number reached 4 x 10(3)/well, half cells was lysed by lysis buffer to extract DNA, the other half was kept on growing to freeze and extract RNA. The knock-out cell colonies first detected by PCR, then confirmed by Southern blot and RT-PCR. All the results show that we have knocked out HPRT gene in three rat fetal neural stem cell colonies from 32 colonies.

[Cloning and analysis of six full-length cDNA similar to sheep KAP6-1 from cashmere goat].

Cashmere is the fiber of kings, produced from the cashmere goat (Capra hircus). Cashmere fabric has little squama. Due to its lightness cashmere feels smooth and silky. An intriguing feature of cashmere structure is multiplicity of the hair keratin proteins with distinctive amino acid compositions. To study the role and regulation of one of these keratins, we used the SMART ( switching mechanism at 5' end of RNA transcript) technology to construct a cDNA library of skin tissue from an Inner Mongolia male cashmere goat. A total of 636 cDNA sequences were obtained by randomly sequenced from 5' of cDNA library. Sequence comparison with the GenBank database confirmed that there are 41 sequences showed high nucleotide sequence identity in the coding region with sheep keratin associated protein 6-1 (KAP6-1). They represent six different cDNAs (The accession numbers in GenBenk are AY310749, AY310750, AY310751, AY310752, AY310753 and AY310754, respectively). They are full-length cDNAs according to the known KAP6-1 genomic gene sequences of sheep. From the nucleotide sequences the open reading frames were identified, that encoded six basic proteins of 82, 84, 71, 71, 83, 83 amino acids, respectively, with a combined glycine and tyrosine content of about 60%. Compared analysis showed that the KAPs from goats shared more than 55.4% identities in nucleotide sequences and more than 79.8% identities in amino acid sequences with each other, and shared highest identities (81.9% approximately 98.8%) with KAP6-1 from sheep. The KAP6s from different animal species shared more than 50% identities in amino acid sequences with each other.

Abrin-a A chain expressed as soluble form in Escherichia coli from a PCR-synthesized gene is catalytically and functionally active.

Abrin-a A chain (ABRaA) is a potent plant toxin, which possesses N-glycosylase activity toward eukaryotic 28S rRNA, and may have potential use in cancer therapy. To improve levels of expression in Escherichia coli, the gene encoding ABRaA was optimized by replacing rare codons with high-frequency ones, and synthesized using two-step PCR. The optimized ABRaA was cloned into the pET-His vector, and highly expressed in cytoplasm of E. coli. The yield of the purified recombinant (r) ABRaA proteins was up to 80 mg/l of induced culture. The rABRaA was one-step purified to homogeneity and its RNA-N-glycosylase ability to inhibit protein biosynthesis in a cell-free system and to depurinate 28S rRNA in rat liver ribosomes was demonstrated in vitro. The MTT assay showed that it also had a killing effect on human hepatoma cell line SMMC-7721 and myeloma cell line Sp2/0. For the first time, ABRaA expressed as soluble form in E. coli from a PCR-synthesized gene is catalytically and functionally active.

[Studies of effects of lipid on rat fetal neural stem cells].

Rat fetal neural stem cells (rFNSCs) was separated from embryo about 14.5-16.5 days, and cultured in DMEM/F12 media with additives and epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF). Effects of lipid on growth and proliferation of rFNSCs was examined by counting the number of neurospheres and incorporation of 3H. The data show that chemical defined lipid improved rFNSCs' growth and cell division. Lipid will be another neural stem cell's culture media's additive.