AIM:To construct a yeast expression system of humanaugmenter of liver regeneration(hALR)and to examine itsbioactivity in vitro.METHODS:With PCR and gene recombination techniques,cDNA of open reading frame of hALR was obtained fromrecombinant plasmid pcDNA3.1-hALR and inserted intoplasmid pPIC9.The cDNA of hALR from recombinant plasmidpPIC9-hALR demonstrated by sequencing was subclonedinto plasmid pPIC9K.The recombinant plasmid pPIC9K-hALR was transformed into GS115 with electroporation.hALR was expressed by GS115 under the induction of 5 mL/Lmethanol and purified with ultrafiltration after it was analyzedby 15% SDS-PAGE and Western blot.The effects of hALRon in vitro proliferation of QGY and HepG_2 cells were evaluatedby ~3H-TdR methods.RESULTS:The correctness and integrity of recombinantplasmids pPIC9-hALR and pPIC9K-hALR were identifiedby restriction digestion,PCR and sequencing methods,respectively.hALR as a secretive protein was successfullyexpressed by GS115.Its molecular weight was about 15 kuand the target protein was about 60% of the total proteinin the supernatant from GS115 with plasmid pPIC9K-hALR.The results of Western blot of hALR showed the specificband.The high qualitative hALR was obtained throughultrafiltration,hALR could stimulate in vitro proliferation ofQGY and HepG_2 cells in a dose-dependent manner,but therewas a difference in reactivity to hALR between QGY and HepG_2.CONCLUSION:The hALR as a secretive protein can besuccessfully expressed by GS115.It may stimulate in vitroproliferation of QGY and HepG_2 cells at a dose-dependentmanner.But QGY and HepG_2 cells have different reactivitiesto hALR.Liu Q,Yu HF,Sun H,Ma HF.Expression of human augmenterof liver regeneration in pichia pastoris yeast and its bioactivityin vitro.World J Gastroenterol 2004;10(21):3188-3190http://www.wjgnet.com/1007-9327/10/3188.asp AIM: To construct a yeast expression system of human valve of liver regeneration (hALR) and to examine its bioactivity in vitro. METHODS: With PCR and gene recombination techniques, cDNA of open reading frame of hALR was obtained from recombining plasmid pcDNA3.1-hALR and inserted intoplasmid pPIC9. The cDNA of hALR was purified by GS115 under induction of 5 mL / L methanol and purified with ultrafiltration after it was analyzed by 15% SDS-PAGE and Western blot.The effects of hALRon in vitro proliferation of QGY and HepG_2 cells were evaluatedby ~ 3H-TdR methods.RESULTS: The correctness and integrity of recombinant plasmids pPIC9-hALR and pPIC9K-hALR were identifiedby restriction digestion, PCR and sequencing methods, respectively. HALR as a secretive protein was successfully expressed by GS115.Its molecular weight w as about 15 kuand the target protein was about 60% of the total protein in the supernatant from GS115 with plasmid pPIC9K-hALR.The results of Western blot of hALR showed the specific band. hQR could stimulate through vitro proliferation ofQGY and HepG_2 cells in a dose-dependent manner, but there was a difference in reactivity to hALR between QGY and HepG_2.CONCLUSION: The hALR as a secretive protein can be successfully harbored by GS115.It may stimulate in vitroproliferation of QGY and HepG_2 cells at a dose-dependent manner. But QGY and HepG2 cells have different reactivitiesto hALR. Liu Q, Yu HF, Sun H, Ma HF. Expression of human augmenter of liver regeneration in pichia pastoris yeast and its bioactivity in vitro. World J Gastroenterol 2004; 10 (21) : 3188-3190http: //www.wjgnet.com/1007-9327/10/3188.asp