Engineering yeast artificial core promoter with designated base motifs

Synthetic biology requires toolbox of promoters to finely tune gene expression levels for building up efficient cell factories. Yeast promoters owned variable core promoter regions between the TATA-box and transcriptional starting site (TSS) at the length mostly around 20-80 bases. This region allowed flexible design of artificial promoter but potentially demand special base motifs to maintain or enhance the promoter's strength.

Here, we designed and screened the base motifs and tested the activities of yeast artificial core promoters. Different 30 bases of artificial sequences led to variable expression levels of CrtY enzyme which determined the lycopene-carotene compositions, represented in the colony-color spectrum of red-orange-yellow. The upstream sequences of two strong promoter P_EXP1 and P_GPD and two starting strains with distinguishable lycopene production levels were utilized to characterize the promoter sequences. Different partition designs of T-rich or G/C-rich base motifs led to distinguishable colony-color distributions. Finally, we screened a champion promoter with a highest 5.5-fold enhancement of lycopene-carotene transformation. Another selected promoter generated a highest beta-carotene production as 7.4 mg/g DCW.

This work offered an approach to redesign promoter with artificial sequences. We concluded that the core promoter region could be designated as 30 bases and different base motifs would enhance or weaken the promoter's strength. Generally, more T-rich elements, higher %T and lower G/C percentage were beneficial to enhance the strength of artificial core promoter.