The present invention relates to a polynucleotide comprising a nucleotide sequence of a promoter region of a gene encoding .alpha. subunit Gm1 of trimeric G-protein, more specifically, said polynucleotide, wherein the nucleotide sequence of a promoter region is, for example, any of the following nucleotide sequences (1) and (2): (1) the nucleotide sequence of SEQ ID NO: 1, and (2) the nucleotide sequence of the nucleotide numbers 603 to 3871 in the nucleotide sequence of SEQ ID NO: 1 and the like.