Ould be an important factor that influenced shRNA silencing activity. But the stem structure of pSuper Cyproconazole vector also influenced its silencing activity (Fig. S4). Overall, the newA Robust shRNA System Used for RNA InterferenceFigure 2. The effects of various loop sequences on shRNA silencing activity. (A) An shRNA scaffold targeted to the HBV conserved sequence “GGUAUGUUGCCCGUUUGUCCU” reported previously was selected and designed as an antisense-loop-sense structure (AS). (B) (C) The two best loops were selected and compared with two well-known loops TTCAAGAGA (used in pSuper) and CTCGAG (used in pLKO.1-puro) for two irrelevant target depression. The HBV target sequence “GGUAUGUUGCCCGUUUGUCCU” and the Gluc target sequence “UCUGUUUGCCCUGAUCUGCAU” were used in (B) and (C) respectively. Statistical significance was determined respectively by comparing shRNAs groups with that containing “TTCTAGAA” loop. Means and standard deviations were generated from 3 independent experiments. The “blank” group represents cells treated with pshOK-basic instead of the shRNA plasmid. The value in the blank group was set at 1.0. doi:10.1371/journal.pone.0056110.gFigure 3. Comparison of the two shRNA construction methods. (A) The shRNA clone method based on one long oligonucleotide (MO). The oligo underlined was synthesized and annealed to its self to form double strands. (B) The shRNA clone method based on two short oligonucleotides (MT). Two short oligonucleotides (underlined) were synthesized and the 5′-end of the oligo containing the loop sequence (TTCTAGAA) phosphorylated by the T4 polynucleotide kinase in the presence of ATP. Then, the two short oligonucleotides were annealed to form double strands. (C) The shRNA cloning efficiency of the two methods was compared. The vector pshOK-basic was digested with Sap I and ligated with the annealed double strand oligos as described above. The “control” group represents the linearized pshOK-basic ligated in the absence of oligos. Means and standard 22948146 deviations were generated from 3 independent experiments. doi:10.1371/journal.pone.0056110.gA Robust shRNA System Used for RNA InterferenceTable 1. Target sequences of the shRNAs.shRNA name ASLacZ-1 ASLacZ-2 ASLacZ-3 ASGluc-1 ASGluc-2 ASGluc-3 AS139 AS618 AS1819 AS1850 AS1856 AS2056 AS2068 AS2090 AS2497 AS3002 AS3083 ASTarget sequence (5′-3′) GCAGUUAUCUGGAAGAUCAGG ML240 biological activity UGGCAGGCGUUUCGUCAGUAU CGGCGACUUCCAGUUCAACAU UCUGUUUGCCCUGAUCUGCAU UGCCUUCGUGCAGUGUUCUGA UGCGACCUUUGCCAGCAAGAU UGCCUUCUGACUUCUUUCCUU CGGGAAUCUCAAUGUUAGUAU GCUGCUAUGCCUCAUCUUCUU UACCAAGGUAUGUUGCCCGUU GGUAUGUUGCCCGUUUGUCCU CCGUUUCUCCUGGCUCAGUUU GCUCAGUUUACUAGUGCCAUU GUUCAGUGGUUCGUAGGGCUU UCGCCAACUUACAAGGCCUUU UCGCAUGGAAACCACCGUGAA AACGACUGACCUUGAGGCAUA UAGGAGGCUGUAGGCAUAAAUdoi:10.1371/journal.pone.0056110.tAfter successfully suppression of the LacZ and Gluc genes using the method described, we tested this approach as a means of combating HBV infections that represent an important public health threat in China. Today there are several high performance nucleotide analogs that can suppress HBV DNA replication, but there are no clinically approved drugs with the capacity of suppressing or preventing the expression of HBV antigens, especially for HBsAg. HBsAg plays important roles in the HBV life cycle and in the establishment of chronic infections [20]. Therefore, HBsAg clearance is critical to the development of successful HBV antiviral therapies. In this study, we utilized our shRNA method to successfully.Ould be an important factor that influenced shRNA silencing activity. But the stem structure of pSuper vector also influenced its silencing activity (Fig. S4). Overall, the newA Robust shRNA System Used for RNA InterferenceFigure 2. The effects of various loop sequences on shRNA silencing activity. (A) An shRNA scaffold targeted to the HBV conserved sequence “GGUAUGUUGCCCGUUUGUCCU” reported previously was selected and designed as an antisense-loop-sense structure (AS). (B) (C) The two best loops were selected and compared with two well-known loops TTCAAGAGA (used in pSuper) and CTCGAG (used in pLKO.1-puro) for two irrelevant target depression. The HBV target sequence “GGUAUGUUGCCCGUUUGUCCU” and the Gluc target sequence “UCUGUUUGCCCUGAUCUGCAU” were used in (B) and (C) respectively. Statistical significance was determined respectively by comparing shRNAs groups with that containing “TTCTAGAA” loop. Means and standard deviations were generated from 3 independent experiments. The “blank” group represents cells treated with pshOK-basic instead of the shRNA plasmid. The value in the blank group was set at 1.0. doi:10.1371/journal.pone.0056110.gFigure 3. Comparison of the two shRNA construction methods. (A) The shRNA clone method based on one long oligonucleotide (MO). The oligo underlined was synthesized and annealed to its self to form double strands. (B) The shRNA clone method based on two short oligonucleotides (MT). Two short oligonucleotides (underlined) were synthesized and the 5′-end of the oligo containing the loop sequence (TTCTAGAA) phosphorylated by the T4 polynucleotide kinase in the presence of ATP. Then, the two short oligonucleotides were annealed to form double strands. (C) The shRNA cloning efficiency of the two methods was compared. The vector pshOK-basic was digested with Sap I and ligated with the annealed double strand oligos as described above. The “control” group represents the linearized pshOK-basic ligated in the absence of oligos. Means and standard 22948146 deviations were generated from 3 independent experiments. doi:10.1371/journal.pone.0056110.gA Robust shRNA System Used for RNA InterferenceTable 1. Target sequences of the shRNAs.shRNA name ASLacZ-1 ASLacZ-2 ASLacZ-3 ASGluc-1 ASGluc-2 ASGluc-3 AS139 AS618 AS1819 AS1850 AS1856 AS2056 AS2068 AS2090 AS2497 AS3002 AS3083 ASTarget sequence (5′-3′) GCAGUUAUCUGGAAGAUCAGG UGGCAGGCGUUUCGUCAGUAU CGGCGACUUCCAGUUCAACAU UCUGUUUGCCCUGAUCUGCAU UGCCUUCGUGCAGUGUUCUGA UGCGACCUUUGCCAGCAAGAU UGCCUUCUGACUUCUUUCCUU CGGGAAUCUCAAUGUUAGUAU GCUGCUAUGCCUCAUCUUCUU UACCAAGGUAUGUUGCCCGUU GGUAUGUUGCCCGUUUGUCCU CCGUUUCUCCUGGCUCAGUUU GCUCAGUUUACUAGUGCCAUU GUUCAGUGGUUCGUAGGGCUU UCGCCAACUUACAAGGCCUUU UCGCAUGGAAACCACCGUGAA AACGACUGACCUUGAGGCAUA UAGGAGGCUGUAGGCAUAAAUdoi:10.1371/journal.pone.0056110.tAfter successfully suppression of the LacZ and Gluc genes using the method described, we tested this approach as a means of combating HBV infections that represent an important public health threat in China. Today there are several high performance nucleotide analogs that can suppress HBV DNA replication, but there are no clinically approved drugs with the capacity of suppressing or preventing the expression of HBV antigens, especially for HBsAg. HBsAg plays important roles in the HBV life cycle and in the establishment of chronic infections [20]. Therefore, HBsAg clearance is critical to the development of successful HBV antiviral therapies. In this study, we utilized our shRNA method to successfully.