Base substitutions in the 5' non-coding regions of two naturally occurring yeast invertase structural SUC genes cause strong differences in specific invertase activities.

Gene SUC4 produced about four fold more invertase activity than did gene SUC5. However, these genes differ in only three positions located in the 5' non-coding region. The difference in gene expression between SUC4 and SUC5 must be due to the G to A transition (position-497) and/or the C to T transition (position -460) in the upstream activator sequences. The sequence TACAAA present in SUC5 can play the same role than the TATAAA box of SUC4.