Xyr1 (xylanase regulator 1) and ACEI are two transcriptional factors that regulate xylanases and cellulases formation in Trichoderma reesei. To investigate the transcriptional regulation of cellulases, DNA binding domains of both Xyr1 and ACEI in T. reesei were expressed from E. coli. Electrophoresis mobility shift assays showed that both formed complexes with the cbh1 promoter fragment (-304 to -18), suggesting that Xyr1 and ACEI may regulate cbh1 expression by bindings to the corresponding sites in the cbh1 promoter.