# Improvement

This year, we made several improvements to existing parts, especially to CI434, BBa_C0056, by constructing CI434ts-TEVsite, BBa_K2969020.

Firstly, we inserted the TEV protease recognition sequence between N-terminal and C-terminal of CI434 so that it can be cleaved by TEV and then lose activity, which can regulate gene expression at both transcriptional and proteolytic levels. As shown in Figure 1 and Figure 2, we can see that CI434-TEVsite and original TEV have little difference. However, when there exists TEV protease, CI434-TEVsite can lose its activity so that the genes expression under CI434-TEVsite can be activated significantly.

Besides, we also developed CI434ts-TEVsite through an evolutionary strategy which use temperature as a screening condition. CI434ts is a heat-inducible ON-transcription factor which is a thermo-sensitive mutation type of CI434 transcription factor, which can regulate gene expression at different temperatures. As shown in Figure 3, when the temperature is high, CI434ts will function and repress its promoter to inhibit the process of under-stream genes transcription more tightly than original CI434.

Therefore, our part, CI434ts-TEVsite have both functions and can be applied in many ways.