“…[5] There are reports, most notably with the a-keto-pipecolyl-amide FK506 analogues, where the linker strongly affects the levels of transcription activation. [9,22,23] Thus, we wanted to compare the activity of the DHFR proteins with Dex ± Mtx CIDs with different chemical linkers. Work with the two-hybrid system for detecting protein ± protein interactions has shown that the nature of the protein chimeras can dramatically influence the activity of the reconstituted transcriptional activator.…”