A nucleic acid construct comprising a chimeric promoter sequence and a cloning site for insertion of a coding sequence in operable linkage with the chimeric promoter, wherein the chimeric promoter sequence comprises: (a) a hCMV immediate early promoter sequence； (b) exon 1 and at least a part of exon 2 of the hCMV major immediate early gene； and (c) a heterologous intron provided in place of the intron A region of the hCMV major immediate early gene.
