AIM:To investigate the role of human La protein in HBVmRNA expression.METHODS:Three human La protein (hLa) specific siRNAexpression cassettes (SECs) containing U6+1 promoter wereprepared via one-step overlapping extension PCR.Aftertransfection with SECs into HepG2 cells,inhibition effectson hLa expression were analyzed by semi-quantitative RT-PCR and Western blotting.Then,effective SECs werescreened out and transfected into 2.2.15 cells,a stable HBV-produdng cell line.HBV surface antigen (HBsAg) and e antigen(HBeAg) secretions into culture media were detected bymicroparticle enzyme immunoassay (MEIA) and HBs and HBemRNA levels were analyzed by semi-quantitative RT-PCR.RESULTS:SEC products containing U6+1 snRNA promoter,and 3 sites of hLa mRNA specific siRNA were obtainedsuccessfully by one-step overlapping extension PCR andcould be directly transfected into HepG2 cells,resulting ininhibition of La protein expression in both mRNA and proteinlevels,among which U6+1-hLa833 was the most efficient,which reduced 18.6-fold mRNA and 89% protein levelrespectively.In 2.2.15 cells,U6+1-hLa833 was also efficienton inhibition of hLa expression.Furthermore,semi-quantitativeRT-PCR showed that HBs and HBe mRNA levels were significantlydecreased by 8- and 66-fold in U6+1-hLa833 transfectedcells compared to control.Accordingly,HBsAg and HBeAgsecretions were decreased partly posttransfection with SECs.CONCLUSION:PCR-based SECs can be used to mediate RNAiin mammalian cells and provide a novel approach to study thefunction of La protein.The inhibition of La protein expressioncan result in a significant decrease of HBV mRNA,which impliesthat the hLa protein is also involved HBV RNA metabolism asone of the HBV RNA-stabilizing factors in human cells. AIM: To investigate the role of human La protein in HBV mRNA expression. METHODS: Three human La protein (hLa) specific siRNA expression cassettes (SECs) containing U6 + 1 promoter wereprepared via one-step overlapping extension PCR.Aftertransfection with SECs into HepG2 cells, inhibition effectson hLa expression were analyzed by semi-quantitative RT-PCR and Western blotting. Chen, effective SECs werescreened out and transfected into 2.2.15 cells, a stable HBV-produdng cell line. HBV surface antigen (HBsAg) and e antigen ) secretions into culture media were detected bymicroparticle enzyme immunoassay (MEIA) and HBs and HBemRNA levels were analyzed by semi-quantitative RT-PCR.RESULTS: SEC products containing U6 + 1 snRNA promoter, and 3 sites of hLa mRNA specific siRNA were obtained successfully one-step overlapping extension PCR and can be directly transfected into HepG2 cells, resulting in inhibition of La protein expression in both mRNA and protein levels, among which U6 + 1-hLa833 was the most ef ficient, which reduced 18.6-fold mRNA and 89% protein level separately.In 2.2.15 cells, U6 + 1-hLa833 was also efficienton inhibition of hLa expression.Furthermore, semi-quantitative RT-PCR showed that HBs and HBe mRNA levels were significantly increased by 8- and 66-fold in U6 + 1-hLa833 transfected cells compared to control. Accredially, HBsAg and HBeAgsecreations were decreased partly post transfection with SECs. CONCLUSION: PCR-based SECs can be used to mediate RNAi in mammalian cells and provide a novel approach to study the function of La protein. inhibition of La protein expression result in a significant decrease of HBV mRNA, which implyhat the hLa protein is also involved in HBV RNA metabolism asone of the HBV RNA-stabilizing factors in human cells.