Screening and identification of interacting proteins with hepatitis B virus core protein in leukocytes and cloning of new gene C1

AIM

To investigate the biological function of HBcAg in pathogenesis of HBV replication in peripheral blood mononuclear cells (PBMCs).

METHODS

HBcAg region was amplified by polymerase chain reaction (PCR) and HBV HBcAg bait plasmid pGBKT7-HBcAg was constructed by routine molecular biological methods. Then the recombinant plasmid DNA was transformed into yeast AH109. After the HBV core protein was expressed in AH109 yeast strains (Western blot analysis), yeast-two hybrid screening was performed by mating AH109 with Y187 containing leukocyte cDNA library plasmid. Diploid yeast cells were plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) (QDO) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) (TDO). The second screening was performed with the LacZ report gene ( yeast cells were grown in QDO medium containing X-alpha-gal). The interaction between HBV core protein and the protein obtained from positive colonies was further confirmed by repeating yeast-two hybrid. After plasmid DNA was extracted from blue colonies and sequenced, the results were analyzed by bioinformatic methods.

RESULTS

Eighteen colonies were obtained and sequenced, including hypermethylated in cancer 2 (3 colones), eukaryotic translation elongation factor 2 (2 colones), acetyl-coenzyme A synthetase 3 (1 colone), DNA polymerase gamma (1 colone), putative translation initiation factor (1 colone), chemokine (C-C motif) receptor 5 (1 colone), mitochondrial ribosomal protein L41 (1 colone), kyot binding protein genes (1 colone), RanBPM (1 colone), HBeAg-binding protein 3 (1 colone), programmed cell death 2 (1 colone). Four new genes with unknown function were identified.

CONCLUSION

Successful cloning of genes of HBV core protein interacting proteins in leukocytes may provide some new clues for studying the biological functions of HBV core protein.

Effect of increased hepatic platelet activating factor and its receptor portal hypertension in CCl4-induced liver cirrhosis

AIM: To evaluate the changes in hepatic platelet activating factor (PAF) and its receptors and their effect on portal pressure of cirrhotic rats induced by CCl₄.

METHODS: A model of liver cirrhosis was replicated in rats by intra-peritoneal injection of CCl₄ for 8 wk. We determined the effect of hepatic PAF and its receptor level on portal and arterial pressure by EIA, saturation binding and RT-PCR technique.

RESULTS: Compared to control rats, cirrhotic rats had higher hepatic PAF levels and output as well as higher plasma PAF levels (P < 0.01, P < 0.01, P < 0.05, respectively). Both hepatic PAF receptor mRNA levels and PAF binding were nearly 3-fold greater in cirrhotic rats (P < 0.01). Portal injection of PAF (1 g/kg WT) increased the portal pressure by 22% and 33% in control and cirrhotic rats, respectively. In contrast, the arterial pressure was decreased in the both groups (54% in control rats and 42% in cirrhotic rats). Injection of the PAF antagonist BN52021 (5 mg/kg WT) decreased the portal pressure by 16% in cirrhotic rats but had no effect in the control rats.

CONCLUSION: The upregulation of the PAF system contributes to hepatic hemodynamic and metabolic abnormalities in cirrhosis, and the increased release of PAF into the circulation has impacts on the systemic hemodynamics.

Cloning and characterization of a novel hepatitis B virus core binding protein C12

AIM: To elucidate the biological function of HBV core antigen (HBcAg) on pathogenesis of hepatitis B, a novel gene C12 coding for protein with unknown function interacting with HBcAg in hepatocytes was identified and characterized.

METHODS: HBcAg bait plasmid pGBKT7-HBcAg was constructed and transformed into yeast AH109, then the transformed yeast was mated with yeast Y187 containing liver complementary DNA (cDNA) library plasmid in 2×YPDA medium. Diploid yeast was plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing X-α -gal for screening twice. After extracting and sequencing of plasmid from blue colonies, we isolated a cDNA clone encoding a novel protein designated as C12 that directly interacted with HBcAg. The interaction between HBcAg and C12 was verified again by re-mating. pEGFP-N1-C12 fluorescent protein fusion gene was transfected in 293 and L02 cell, and observed by fluorescent microscope. MTT reduction assay was used to study the action of C12 protein effect on metabolism of mammal cell. Yeast two-hybrid and cDNA microarray were performed to search binding protein and differential expression genes regulated by C12 protein.

RESULTS: C12 gene was screened and identified by yeast two-hybrid system 3. The interaction between HBcAg and the novel protein coded by the new gene C12 was further confirmed by re-mating. After 48 h, fluorescence of fusion protein could be observed steadily in the 293 and L02 cell plasma. Under MTT assay, we found that the expression of C12 did not influence the growth of liver cells. Seventeen differential expression genes in HepG2 cells transfected with C12 protein expression plasmid by cDNA microarray, of which 16 genes were upregulated and 1 gene was downregulated by C12 protein. Twenty-one colonies containing 16 different genes coding for C12 protein binding proteins were isolated by yeast two-hybrid, there were 2 new genes with unknown function.

CONCLUSION: The novel protein C12 is located in cell plasma, and its overexpression has no significant effect on the metabolism of liver cell. It interacts with many proteins in hepatocytes and may be involved in many processes of gene expression.

Autonomous activation of hepatitis B virus large surface protein

AIM: To construct the yeast expression vector of hepatitis B virus large surface protein (LHBs), and to study its autonomous activation.

METHODS: The Matchmaker GAL4 two-hybrid technique was used. The LHBs, pre-S1, pre-S2 and SHBs genes were amplified by polymerase chain reaction (PCR) with respective primers. The amplified PCR fragments were then subcloned into the EcoR I/BamH I sites (5'ands) of pGBKT7 vector to obtain the expression vectors including pGBKT7(-)-LHBs, pGBKT7(-)-preS1, pGBKT7(-)-preS2 and pGBKT7(-)-SHBs. This vectors were identifed by PCR and digestion of EcoR I/BamH I. After the constructed vectors were transformed into yeast AH109, the yeast cells were plated on synthetic dropout nutrient medium (SD/-Trp and SD/-Trp-His-Ade) containing x-a-gal for testing their autonomous activation.

RESULTS: The yeast expression vectors were constructed. The yeast cells transformed with pGBKT7-LHB and pGBKT7-preS1 vectors could grow well on both of the media. However, cells transformed with pGBKT7-preS2 and pGBKT7-SHBs vectors could only grow on the SD/-Trp medium.

CONCLUSION: The LHBs functions as a transcriptional transactivator, and serves as the functional GAL4 activation domain (AD) to activate transcription of reporter genes (ADE2, HIS3, MEL1 and LacZ). The autonomous activation of LHBs roots in its pre-S1 domain.

[Mutual interaction between hepatitis B virus antigen and metallothionein]

OBJECTIVE

To screen and identify the protein interacting with HBV antigen in hepatocytes. Then investigate the biological functions of hepatitis B virus antigen in the pathogenesis of hepatitis B and seek effective methods to prevent and treat it.

METHODS

The yeast two-hybrid system-3 technique was used to construct HBV PreS2, HBeAg, HBcAg, HBxAg bait plasmids. The bait plasmids transformed the yeast AH109 and expressed themselves in it. After being identified by SDS-PAGE and Western blot, the AH109 yeast was mated with yeast Y187 containing liver cDNA library plasmid in 2 x YPDA medium to form diploid yeast and was then plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing x-alpha-gal for screening. Plasmids of blue colonies were extracted and transformed into Escherichia coli, then analyzed by DNA sequencing and bioinformatics. To further prove the interaction between HBV antigen and metallothionein, translation was performed by using reticulocyte lysate and coimmunoprecipitation was displayed in vitro.

RESULTS

Genes coding for HBV antigen binding protein were successfully cloned and metallothionein was found in that protein. The interaction between HBeAg, HBcAg and HBxAg and metallothionein were further proved by coimmunoprecipitation in vitro.

CONCLUSION

The interaction between HBV antigen and metallothionein indicates that metallothionein may participate in the pathogenesis of hepatitis B

Screening and identification of genes trans-regulated by a novel HBeAg binding protein E-18 with microarray assay

AIM: To investigate the biological functions of a novel hepatitis B virus e antigen (HBeAg) binding protein E-18, and to use cDNA microarray technique to screen genes regulated by E-18.

METHODS: A novel gene E-18 coding for HBeAg was screened and identified by using yeast two-hybrid system 3 and co-immunoprecipitation technique. The E-18 coding DNA fragment was amplified by reverse transcription polymerase chain reaction (RT-PCR) technique from HepG2 cell. The expressive vector of pcDNA3.1-E-18 was constructed by routine molecular biological methods. The HepG2 cells were transfected with pcDNA3.1(-) and pcDNA3.1-E-18, respectively by using lipofectamine. The total RNA was isolated and reverse transcribed. The cDNA of each sample were subjected to microarray screening with 1 152 cDNA probes and analyzed by bioinformatics.

RESULTS: E-18 cDNA sequence was obtained and identified by yeast two-hybrid screening and bioinformatics analysis. The expressive vector was constructed and confirmed by DNA sequencing analysis and restriction enzyme digestion. High quality mRNA and cDNA of transfected HepG2 cells had been prepared and successful microarray screening conducted. From the scanning results, there were 52 differential expression genes, of which 36 genes were down-regulated, and 16 genes were up-regulated.

CONCLUSION: Microarray technique is successfully used to screen the genes trans-regulated by E-18. The expression of E-18 protein affects the expression spectrum of HepG2 cell.

Effects of HCBP6 protein on transact-ivating function of HCV core protein

AIM: To study the inhibitory effects of HCBP6 on the transactivating effect of HCV core protein.

METHODS: The recombinant vectors expressive HCV core protein and HCBP6 protein were constructed, respectively, by routine molecular techniques. The hepatoblastoma cell line HepG2 were co-transfected. The chloramphenicol transferase (CAT) expressive levels under the SV40 early promoter were determined by an enzyme-linked immuno-sorbent assay (ELISA) kit.

RESULTS: The recombinant vectors of pcDNA3.1(-)-HCBP6 and pcDNA3.1(-)-core were constructed, and demonstrated correctly by restriction enzyme digestion and sequencing analysis. The hepatoblastoma cell line HepG2 was transfected with the vector alone or combined, respectively. The expression level of CAT indicated that the inhibitory rate was 40.4%-62.3%.

CONCLUSION: The expression of HCBP6 has inhibitory effects on the transacting activity of HCV core protein.

Identification and sequence analysis of a Macaca fascicularis homologous gene to human hepatitis B viruse antigen binding protein E-19

AIM: To explore the biological and immunoregulatory functions of hepatitis B e antigen (HBeAg) which is a secreted nonparticulate version of the viral nucleocapsid hepatitis B core antigen (HBcAg), yeast-two hybrid technique was performed to seek proteins in hepatocytes interacting with HBeAg and a novel gene named as E-19 was identified. To clone E-19 homologous gene from different species, a Macaca fascicularis homologous gene E-19 was identified by bioinformatics.

METHODS: HBeAg bait plasmid was constructed and transformed into yeast AH109 (a type). AH109 was mated with yeast cells Y187 (type) containing liver cDNA library plasmid pCAT2 in 2×YPDA medium. Plasmid of true positive blue colonies were extracted and analyzed by DNA sequencing and a new human gene E-19 was identified. A Macaca fascicularis homologous gene E-19 was identified by bioinformatics methods.

RESULTS: A Macaca fascicularis homologous gene E-19 was identified by bioinformatics. The Macaca fascicularis homologous gene E-19 was consisted of 378 nt and encoded a protein of 125 aa.

CONCLUSION: Human gene E-19, a HBeAg interacting proteins in hepatocytes, is successfully cloned by yeast-two hybrid technique and a Macaca fascicularis homologous gene E-19 is identified by bioinformatics.

Identification and characterization of retinol dehydrogenase 11 as a hepatitis C virus core protein-binding protein by yeast-two hybrid technique

AIM: To screen the hepatocyte protein interacting with HCV core protein.

METHODS: By using HCV core protein as a bait, yeast-two hybrid system 3 was employed for screening and identification of HCV core protein-binding proteins from a hepatocyte cDNA library expressed in yeast cells. The protein-protein interaction was confirmed by back-cross experiment, and the inserts of the expressive vectors were sequenced and analyzed by bioinformatics methods.

RESULTS: Among them we identified retinol dehydrogenase 11(RDH11/androgen- regulated short-chain dehydrogenase/reductase 1 (ARSDR1) as a HCV core protein-interacting protein. This is the first time, to the best of our knowledge, to know the fact that there are interactions of HCV core protein-retinol dehydrogenase 11.

CONCLUSION: The identification of retinol dehydrogenase 11 as the HCV core protein binding partner paves a new way for further understanding of the pathogenesis of HCV infection.

Identification and sequence analysis of mouse homologous gene coding for hepatitis C virus non-structural protein 5A-binding protein 37

AIM: To clone murine homologous gene to human NS5ABP37 gene, and to elucidate its biological functions and the possible effects in the pathogenesis of hepatitis C virus (HCV) infection.

METHODS: Yeast-two hybrid system was employed to screen the human liver cDNA library by using non-structural protein 5A (NS5A) of hepatitis C virus (HCV) as the bait. According to the homologous role between the species, a murine NS5ABP37 homologous to human NS5ABP37 was deduced by bioinformatics methods. The primary sequence of murine NS5ABP37 was searched for conserved domains by online tools of GeneBank.

RESULTS: Human NS5ABP37 was screened and cloned from human liver cDNA library by yeast-two hybrid system 3. The murine NS5ABP37 was deduced by bioinformatics methods. The open reading frame (ORF) of murine NS5ABP37 consisted of 1 488 nt encoding a protein of 495 amino acids. Calculated molecular weight was 54 583.67 dalton and predicted pI was 4.70. From the homologous protein search, murine NS5ABP37 was demonstrated homologous to leukocyte antigen related (LAR) protein precursor. The sequence of murine NS5ABP37 was deposited into GenBank, and the accession number was AY234860.

CONCLUSION: Successful identification and cloning of murine NS5ABP37, which is homologous to LAR protein precursor, paves a way for elucidating the biological function of murine NS5ABP37 and pathogenesis of hepatitis C virus infection.

Screening and cloning of human gene 5 transactivated by nonstructural protein 5A of hepatitis C virus

AIM: Human gene 5 transactivated by nonstructural protein 5A of hepatitis C virus (NS5ATP5) is a kind of protein with unknown function from the study with suppression subtractive hybridization (SSH). To investigate the biological function of NS5ATP5, we performed yeast-two hybrid to seek for proteins in leucocytes interacting with NS5ATP5.

METHODS: NS5ATP5 bait plasmid was constructed by ligating the gene of NS5ATP5 into pGBKT7, then transformed into yeast AH109 (a type), the transformed yeast mated with yeast Y187 (α type) containing leucocyte cDNA library plasmid in 2×YPDA medium. Diploid yeast was plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing x-α-gal for selection and screening. After extracting and sequencing of plasmids from blue colonies, we underwent sequence analysis by bioinformatics.

RESULTS: Ten colonies were sequenced. Among them, 8 colonies were genes with known functions and two colonies were new genes.

CONCLUSION: The preliminary successful cloning of gene of protein interacting with NS5ATP5 paves the way for studying the physiological function of NS5ATP5 and associated protein.

Gene expression profile of HepG2 cell transfected with a novel gene C-12 coding for HBcAg binding protein

AIM: To study the biological function of a novel hepatitis B virus core antigen binding protein C-12, and to analyze the gene expression profiles of HepG2 cell transfected with C-12 gene.

METHODS: C-12 gene was screened and identified by using yeast two-hybrid system 3 technique. Full-length encoding frame C-12 and its amino acid sequences was identified using bioinformatics method and the recombined eukaryotic expression plasmid pcDNA3.1(-)-C-12 was constructed. cDNA microarray technology was employed to detect the mRNA from HepG2 cells transfected with pcDNA3.1(-)-C-12 and pcDNA3.1(-), respectively.

RESULTS: According to yeast two-hybrid screening and the bioinformatics analysis results, C-12 cDNA sequence was identified. Among 1152 genes, there were 17 differences, of which 16 genes were upregulated and 1 gene were downregulated in HepG2 cells transfected with C-12 protein expression plasmid. These genes differentially regulated by C-12 protein included human genes encoding proteins involved in cell signal transduction, cell proliferation and differentiation, and cell growth regulation.

CONCLUSION: Overexpression of C-12 affects the expression profile of HepG2 cells. The results prove some clues for further clarifying the molecular biology processes of hepatocytes during the interaction between HBV core protein and C-12.

Genes trans-regulated by a novel hepatitis B virus preS2 antigen binding protein S2-29 by cDNA microarray

AIM: To study the biological functions of a novel hepatitis B virus preS2 antigen binding protein S2-29, and to analyze the gene expression profiles of HepG2 cell transfected with S2-29 gene.

METHODS: S2-29 gene was screened and identified by using yeast two-hybrid system 3 and coimmunoprecipita-tion technique. Full-length encoding frame S2-29 and its amino acid sequences were identified by using bioinformatics method and the recombined eukaryotic expression plasmid pcDNA3.1(-)-S2-29 was constructed and transfected into HepG2 cells. Total mRNA was isolated from the HepG2 cells transfected with pcDNA3.1(-) and pcDNA3.1(-)-S2-29, respectively. cDNA microarray was employed for detecting and analysing of mRNA from the HepG2 cells.

RESULTS: S2-29 cDNA sequence was obtained and identified by yeast two-hybrid screening and the bioinformatics analysis. Among 1 152 genes, there were 10 differences, of which 9 genes were upregulated and 1 gene were downregulated in HepG2 cells transfected with S2-29 protein expression plasmid. These genes differentially down-regulated by S2-29 protein included eukaryotic translation elongation factor 2, MAP-kinase activating death domain, glutathione peroxidase 5, gelsolin-like capping protein (actin filament), NDRG family member 2, prosaposin, SUMO-1 activating enzyme subunit 1, insulin receptor and a novel protein.

CONCLUSION: Microarray technique is successfully used to screen the genes trans-regulated by S2-29, which brings some new clues for studying the trans-regulation and biological function of S2-29.

Screening and identification of genes trans-regulated by a novel HBeAg binding protein E-36 with cDNA microarray assay

AIM: To investigate the biological functions of a novel hepatitis B virus e antigen (HBeAg) binding protein E-36, and to screen genes regulated by E-36.

METHODS: The E-36 coding DNA fragment was amplified by reverse transcription polymerase chain reaction (RT-PCR) technique from HepG2 cell. The expressive vector of pcDNA 3.1-E-36 was constructed by routine molecular biological methods. The HepG2 cells were transfected by pcDNA3.1(-) and pcDNA3.1-E-36, respectively by using lipofectamine. The total RNA was isolated and reverse transcribed. The cDNAs were subjected to microarray screening with 1 152 cDNA probes.

RESULTS: The expressive vector was constructed and confirmed by restriction enzyme digestion and DNA sequencing analysis. High quality mRNA and cDNA of transfected HepG2 cells were prepared and successful microarray screening conducted. From the scanning results, 20 genes were found to be up-regulated, including PTH-responsive osteosarcoma B1 protein, slit homolog 2, nuclear factor of kappa light polypeptide gene enhancer in B-cells 1, interleukin 3 receptor, caspase 2, angiotensin I converting enzyme, Low density lipoprotein 1, interkeukin 6, T-cell receptor rearranged beta chain gene V-region, activator of NFB, tumor suppressing subtransferable candidate 1, cyclin-dependent kinase-like 2, sialyltransferase 8, glutamate receptor, metabotropic 7, and 5 novel genes. Expression of the gene of eukaryotic translation elongation factor 2 could be down-regulated by E-36 protein.

CONCLUSION: The expression of E-36 protein affects the expression spectrum of HepG2 cell. The microarray is an important technique for the study of transactivating effects for viral proteins.

Screening and identification of a novel gene coding for hepatitis B virus core antigen interacting protein C-12 in hepatocytes

AIM

Hepatitis B virus(HBV) core protein (HBcAg) is present in the nucleus and cytoplasm of infected hepatocytes. Phosphorylation of HBcAg was a prerequisite for pregenomic RNA encapsidation into viral capsids. HBcAg capsids are extremely immunogenic and can activate naive B cells by cross-linking their surface receptors and HBcAg-specific CD4(+) T-cell responses are believed to play an important role in the control of human HBV infection. To investigate the complex biological functions of HBcAg, we employed yeast-two hybrid technique to screen proteins in hepatocytes interacting with HBcAg.

METHODS

HBcAg gene was amplified by polymerase chain reaction (PCR). The pGBKT7-HBcAg bait plasmid was constructed by using yeast-two hybrid system 3 and transformed into yeast cells AH109, then mated with yeast cells Y187 containing liver cDNA library plasmid in 2×YPDA medium. Diploid yeast was plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing x-α-gal for selection two times. After extracting and sequencing of plasmid from blue colonies, we conducted bioinformatics analysis. Primers of new gene were designed according to the information in GenBank and used to amplify the complete sequence of new gene C-12. Gene of C-12 was ligated into another yeast expression vector pGADT7 and transformed into yeast cell Y187 and mated with yeast cell AH109 containing pGBKT7-HBcAg bait plasmid to further verify the interaction between HBcAg and the novel protein coded by the new gene C-12.

RESULTS

Sixteen colonies were sequenced. Among them, there were four new genes with unknown function. The complete sequence of new gene C-12 was successfully amplified from the mRNA of HepG2 cell by reverse transcription polymerase chain reaction(RT-PCR). The interaction between HBcAg and the novel protein coded by the new gene C-12 was further confirmed by re-mating.

CONCLUSION

Genes of HBcAg interacting proteins in hepatocytes were successfully cloned. The findings of new genes coding for HBcAg associated proteins pave the way for studying the biological functions of HBcAg.

Cloning and identification of human gene 1 transactivated by hepatitis B virus X antigen

AIM

To study the transactivation effects of HBxAg, and clone the target genes of HBxAg transactivating effects, in order to help understand the mechanism of pathogenesis of HBxAg.

METHODS

Polymerase chain reaction (PCR) was employed to amplify the coding sequence of HBxAg. The hepatoblastoma cell HepG2 was transfected by pcDNA3.1(-) and pcDNA3.1(-)-X, respectively. Total mRNA was purified from the HepG2 cells transfected and suppression subtractive hybridization(SSH) method was used to analyze the differentially expressed DNA sequence between the two groups. The sequences were searched for homologous DNA sequence from GenBank. The new DNA sequence was confirmed and the full-length coding sequence was identified according to the Kozak rule and the existence of polyadenyl signal sequences. Reverse transcription PCR (RT-PCR)was used to amplify the new gene by using mRNA from HepG2 cell as the template. The coding sequence for the new gene was deduced according to the nucleotide sequence.

RESULTS

PCR technique was employed to amplify the coding sequence for HBxAg by using pCP10 plasmid containing whole HBV genome as the template. The recombinant plasmid expressing HBxAg was confirmed by restriction enzyme digestion and sequencing. HepG2 cells were transfected with pcDNA3.1(-) and pcDNA3.1(-)-X by lipofectamine, respectively. Total mRNA was purified from transfected HepG2 cell, and suppression subtractive hybridization method was used for the screening and identification of differentially expressed genes by these two cell groups. After sequencing, each DNA sequence was compared with the genes deposited in the GenBank and the new gene with no homology with known genes in this database was identified. Electric polymerase chain reaction was conducted for the cloning of the full-length DNA of the new gene and in conjunction with Kozak rule and the existence of polyadenyl signal sequence. RT-PCR technique was used to amplify the new gene, named as XTP1, from the mRNA of HepG2 cells. The sequence for the XTP1 gene was deposited into GenBank, and the accession number is AF488828.

CONCLUSION

A new gene named XTP1 which is transac-tivated by hepatitis B virus X protein has been successfully cloned by molecular biological methods. These results pave the way for the study of the molecular mechanism of HBxAg transactivating effects and the development of new therapy for chronic hepatitis B.

Cloning of gene 1 transactivated by C-terminally truncated middle surface protein of hepatitis B virus

AIM

To investigate the transactivation effects of C-terminally truncated middle surface protein (MHBst) of hepatitis B virus (HBV) by differential display method. To clone new gene with unknown function that could be transactivated by MHBst with suppression subtractive hybridization (SSH), and pave the way for the study and better understanding of the transactivation effects of MHBst.

METHODS

Polymerase chain reaction (PCR)technique was employed to amplify the coding sequence of MHBst, and the expressive vector pcDNA3.1-MHBst was constructed by routine molecular biological method. The differentially expressed genes were screened and identified by SSH method between the HepG2 cells transfected with pcDNA3.1-MHBst and the vector pcDNA3.1, respectively. Bioinformatics techniques were used to search homologously expressed sequence tag (EST) and full-length coding sequence transactivated by MHBst. The mRNA was purified from HepG2 cells and the DNA fragment was amplified by reverse transcription PCR (RT-PCR) technique. The coding sequence was analyzed by bioinformatics. The new gene transactivated by MHBst was designated as target gene 1 transactivated by truncated middle surface protein of HBV (TTP1).

RESULTS

The expressive vector pcDNA3.1-MHBst was constructed and confirmed by restriction enzyme digestion and sequencing. SSH method was employed for the screening and identification of the differentially expressed genes from the HepG2 cells transfected with pcDNA3.1-MHBst and pcDNA3.1, respectively. Among the target genes, we identified a new gene with unknown function and deposited its sequence into GenBank. From the homology search, we evaluated this gene as a new gene with unknown function.

CONCLUSION

The gene 1 transactivated by C-terminally truncated middle surface protein of hepatitis B virus was identified.

Screening and identification of a novel gene coding for hepatitis B virus pre-S2 antigen interacting protein S2-29

AIM

The Pre-S2 region of hepatitis B virus (HBV) has been reported to have complex biological functions. It has human polymerized albumin receptor (PAR) activity, which correlates with viral replication, and it can induce neutralization antibody. As an important part of truncated middle surface proteins (MHBs), the Pre-S2 domain binds PKC alpha/beta and triggers a PKC-dependent activation of the c-Raf-1/MAP2-kinase signal transduction cascade, resulting in activation of transcription factors such as AP-1 and NF-kB. To investigate the biological function of hepatitis B virus (HBV) Pre-S2 protein, we used yeast two-hybrid technique to screen proteins interacting with HBV Pre-S2 antigen in hepatocytes.

METHODS

The HBV Pre-S2 gene was amplified by polymerase chain reaction (PCR) and cloned into yeast expression vector PGBKT7 to construct HBV Pre-S2 bait plasmid. The bait plasmid was transformed into yeast AH109 and mated with yeast Y187 containing liver cDNA library plasmid in 2×YPDA medium. Diploid yeast was plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing X-α-gal for selection and screening. After being extracted and sequenced, genes were analyzed by bioinformatics. The complete sequence of new gene S2-29 was amplified from the mRNA of HepG2 cell by reverse transcription polymerase chain reaction (RT-PCR) and cloned into pGADT7, then translated by using reticulocyte lysate and analysed by immunoprecipitation technique in vitro.

RESULTS

Twenty-six colonies were obtained, among them two colonies were new genes with unknown function and no homeobox genes were found in Genbank by blast. The complete sequence of new gene S2-29 could be amplified from the mRNA of HepG2 cell and the interaction between HBV Pre-S2 antigen and S2-29 was further confirmed by coimmunoprecipitation technique.

CONCLUSION

Genes of HBV Pre-S2 interacting proteins were successfully screened. A novel gene S2-29 was cloned and could express in HepG2 cell. The HBV Pre-S2 antigen could interact with S2-29, which brings new clues for studying the biological functions of HBV Pre-S2 and the pathogenesis of HBV infection.

Screening and identification of a novel hepatitis B virus e antigen binding protein E-19 in hepatocytes by yeast two-hybrid technique

AIM

The hepatitis B precore Ag (HBeAg) is a secreted nonparticulate version of the viral nucleocapsid hepatitis B core Ag (HBcAg), and its function is unknown. Some researchers have proposed that the HBeAg may have an immunoregulatory function in promoting viral persistence and is associated with immunologic tolerance. To investigate biological functions of hepatitis B virus e protein(HBeAg), yeast two-hybrid technique was employed to seek proteins in hepatocytes interacting with HBeAg.

METHODS

HBeAg bait plasmid was constructed by ligating HBeAg gene with yeast expression vector pGBKT7, then transformed into yeast AH109 (a type). The transformed yeast cells were amplified and mated with yeast cells Y187(α type) containing liver cDNA library plasmid pCAT2 in 2×YPDA medium. Diploid yeast cells were plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing x-α-gal for selection twice. Plasmid of true positive blue colonies were extracted and analysed by DNA sequencing and blast in GenBank. After the complete sequence of new gene E-19 was amplified from the mRNA of HepG2 cell by RT-PCR and cloned into pGADT7 vector, the recombined plasmid was translated by using reticulocyte lysate and analysed by immunoprecipitation technique in vitro together with HBeAg.

RESULTS

Twenty genes in thirty nine positive colonies were obtained, there were five new genes.The complete sequence of new gene E-19 was successfully amplified from the mRNA of HepG2 cell by RT-PCR. The interaction between HBeAg and expression products of new gene E-19 was further confirmed by immunoprecipitation technique.

CONCLUSION

Genes of HBeAg interacting proteins in hepatocytes were successfully cloned and HBeAg could bind with the protein expressed by new gene E-19.

Cloning of a gene coding for novel mutant of asialoglycoprotein receptor 2 binding to hepatitis B virus X protein in hepatocytes

AIM

The pathogenesis of HBV-induced malignant transformation is incompletely understood. The X protein of hepatitis B virus (HBxAg) is a multifunctional protein that can influence a variety of signal transduction pathways within the cell and is essential for establishing natural viral infection, it also has been implicated in the development of liver cancer associated with chronic infection. Further understanding of the interaction between HBxAg and proteins in hepatocytes is of great significance for the prevention of the development of hepatocellular carcinoma (HCC).

METHODS

HBxAg bait plasmid was constructed by ligating the HBxAg gene with a yeast expression vector pGBKT7, then transformed into yeast AH109 (a type). The transformed yeast cells were amplified and mated with yeast cells Y187(α type) containing liver cDNA library plasmid pCAT2 in 2×YPDA medium. Diploid yeast cells were plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing x-α-gal for selection twice. Plasmid of true positive blue colonies was extracted and analysed by DNA sequencing and blast in GenBank. After the complete sequence of the novel mutant of asialoglycoprotein receptor 2 (ASGPR2) was amplified from the mRNA of HepG2 cell by reverse transcription polymerase chain reaction (RT-PCR) and cloned into pGADT7 vector, the recombined plasmid was translated by using reticulocyte lysate and analysed by immunoprecipitation technique in vitro together with HBxAg.

RESULTS

Eighteen genes in forty-one positive colonies were obtained, one of them is a novel mutant of ASGPR2, which is 80 % homologous to natural ASGPR2. The complete sequence of the mutant was amplified from the mRNA of HepG2 cell by RT-PCR successfully. The interaction between HBx and ASGPR2 mutant was further confirmed by immunoprecipitation technique.

CONCLUSION

Interaction between HBx and ASGPR2 mutant can be observed in both yeast cell and in vitro.

Cloning of genes transactivated by NS3 protein of HCV with suppressive and subtractive hybridization

AIM

To construct a subtractive cDNA library of genes transactivated by NS3 protein of hepatitis C virus (HCV) with suppressive and subtractive hybridization technique and clone genes associated with transactivation.

METHODS

The mRNA was isolated from HepG2 cells transfected with pcDNA3.1(-)-NS3, and pcDNA3.1(-) empty vector, respectively; cDNA was synthesized. After digestion with restriction enzyme RsaI, cDNA fragments were obtained by restriction enzyme RsaI digestion. Tester cDNA was then divided into two groups and ligated to the specific adaptor 1 and adaptor 2, respectively. After tester cDNA was hybridized with driver cDNA twice and underwent two times of nested PCR, amplified cDNA fragments were subcloned into T/A plasmid vectors to set up the subtractive library. Amplification of the library was carried out with E. coli strain JM109. The cDNA was sequenced and analyzed in GenBank with Blast search after PCR.

RESULTS

The amplified library contained 70 positive clones. Results of PCR study indicated that 56 clones had inserts of 200-1 000 bp in length. Sequence analysis suggested that six novel cDNA sequences might be target genes transactivated by NS3 protein.

CONCLUSION

The subtractive library of genes transactivated by NS3 protein of HCV was constructed successfully.

Screening of HBcAg interacting proteins in hepatocytes with yeast-two hybrid technique

AIM

To screen proteins in hepatocytes interacting with hepatitis B virus core protein (HBcAg) with yeast-two hybrid technique for investigating the biological functions of HBcAg.

METHODS

The HBcAg gene was amplified by polymerase chain reaction (PCR) and HBcAg bait plasmid was constructed with yeast-two hybrid system 3, then transformed into yeast AH109. The transformed yeast mated with yeast Y187 containing liver cDNA library plasmid in 2×YPDA medium. Diploid yeast was plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing X-α-gal for selecting two times and screening. After extracting and sequencing of plasmid from blue colonies, the results were analyzed by bioinformatics.

RESULTS

Sixteen colonies were sequenced, of which, two colonies were metallothionein 2A, one NAD(P)H dehydrogenase, one complement component 8 a polypeptide, one retinoic acid receptor responder (tazarotene induced), one cytochromeb, one cytochrome c oxidase subunit II , one albumin, two DAZ associated protein 2, two mitochondrial ribosomal protein L41 and four new genes with unknown function.

CONCLUSION

Genes of HBcAg interacting proteins in hepatocytes were successfully cloned and the results provided some new clues for studying the biological functions of HBcAg and its associated proteins.

Screening and cloning of gene encoding HBeAg interacting protein in hepatocytes

AIM

To screen hepatic proteins interacting with hepatitis B virus e antigen (HBeAg) with yeast-two hybrid technique for investigating the function of HBeAg protein.

METHODS

HBeAg bait plasmid was constructed by ligating the HBeAg gene with plasmid pGBKT7, then transformed into yeast α-AH109. The transformed yeast cells were amplified and mated with yeast cells α-Y187 containing liver cDNA library plasmid pCAT2 in 2×YPDA medium. Diploid yeast cells were plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing x-α-gal for selecting twice and screening. After extracting plasmid from blue colonies, plasmid was transformed into competence E.coli and analyzed by DNA sequencing. Twenty genes were obtained from 39 positive colonies, which included five new genes.

RESULTS

Twenty genes in thirty nine positive colonies were obtained including three metallothionein 2 A, eight complement component 8 alpha polypeptide, one complement component 1q, one complement factor H, one retinoic acid receptor responder (tazarotene induced), two cytochrome b, three D-amino-acid oxidase, three ferritin light polypeptide, two NAD(P)H dehydrogenase b, four aldolase B, one CD81, one syndecan 1, one 3-hydroxy-3-methylglutaryl-Coenzyme A synthase 2, one dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1A transcript variant 1, one 3-hydroxysteroid epimerase, one ATP synthase 6 and five new genes.

CONCLUSION

Genes encoding HBeAg interacting proteins in hepatocytes were successfully cloned and the results provided some new clues for studying the biological functions of HBeAg and its associated proteins.

Screening of gene encoding of hepatic proteins interacting with Hcbp6 via yeast two hybridization

AIM

To seek for hepatic proteins that interacted with protein encoded by Hcbp6 for exploring the biological function of Hcbp6.

METHODS

Hcbp6 gene was introduced into pGBKT7, and then transformed into yeast AH109, which was mated with yeast Y187 (αtype) containing liver cDNA library plasmid in 2×YPDA medium. Diploid yeast was plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing x-α-gal. Plasmids were extracted from positive colonies, and sequence analysis was performed by bioinformatics.

RESULTS

Four kind of proteins including paralemmin, Ran binding protein 2, transmembrane transporting protein and albumin were identified to interact with Hcbp6 specifically.

CONCLUSION

Hcbp6 proteins may belong to or be associated with formation of secretary proteins, more study needs to be done for clarifying its biological function.

Gene expression profile of HepG2 cell transfected with hepatitis C virus coreprotein-binding protein6 gene

AIM

To screen and clone genes of hepatic protein interacting with hepatitis C virus (HCV) core protein and analyze the gene expression profiles of HepG2 cell transfected with HCV coreprotein-binding protein6 (HCBP6) gene.

METHODS

Using yeast two-hybrid system3, bait plasmid of HCV coreprotein was constructed and genes encoding HCV coreprotein-binding protein were screened and identified. One gene named HCBP6 was identified. Humanfull-length encoding gene of HCBP6 and its amino acid sequences were identified by bioinformatics method, and there combined expression plasmidpc DNA3. 1(-)-HCBP6 was constructed. mRNA from HepG2 cell stransfected with pcDNA3. 1(-)-HCBP6 and the empty vector were detected with cDNA microarray, respectively.

RESULTS

Human HCBP6 cDNA sequence was identified. The coding sequence for human HCBP6 consists of 456 nt and its protein consists of 152 aa. Twenty of 1152 gene sobtained from gene expression profile analysis differed from those in GenBank, in which 13 genes were up-regulated and 7 genes were down-regulated in HepG2 cells transfected with HCBP6 plasmid. These genes differentially regulated by HCBP6 protein included human genes encoding proteins involved in signal transduction, cell proliferation, differentiation, and growth regulation.

CONCLUSION

The bioinformatics combined yeast two hybrid technique is a powerful method for screening and analysis of genes of hepatic protein interacting with HCV coreprotein. The findings obtained by cDNA microarray technique provided significant data for preliminary understanding of the biologica lfunction of new gene, and also provided some clues for furthe rclarifying the molecular biological processes of hepatocytes in interaction between HCV core protein and HCBP6.