POU-M2 is a homeodomain transcription factor which plays important roles in the development and silk synthesis of Bombyx mori.In this study,we expressed,purified and characterized POU-M2 and studied its transcription regulation on fibroin heavy chain gene of Bombyx mori.Gel filtration showed POU-M2 existed as a dimer in solution.Far-UV circular dichroism spectra indicated POU-M2 had a well-definedα-helix structure and theα-helix content was about 26.4%.The thermal unfolding transition of POU-M2 was a cooperative process.Tm,ΔH and ΔS were 45.15 ± 0.2℃,138.4 ± 0.5 KJ/mol and 0.4349 ± 0.04KJ/(mol· K),respectively.Western blotting analysis indicated the expression level of POU-M2 increased slightly from day 3 to day 7 of the fifth instar larvae in the posterior silk gland.POUM2 was positioned in the nucleus of cells.The luciferase reporter assay demonstrated POU-M2 could stimulate the promoter activity of fibroin heavy chain gene,and the activation effect was dependent on the amount of POU-M2.Our study suggested POU-M2 may be involved in the transcriptional regulation of fibroin heavy chain gene.These findings expand toward a better understanding of the structure of POU-M2 and its function in silk synthesis of Bombyx mori.