The initiation of transcriptional rewiring is influenced by changes in both the cis- and trans-regulatory elements. However, the process on how perturbations in trans-acting elements instigate transcriptional rewiring remains elusive. Previous report showed that Sef1 in Lachancea kluyveri (LkSef1) facilitates non-functional binding to its major target genes. On the other hand, fusing LkSef1 with the transcriptional activator VP16 not only increased its basal activation but also conferred control to other genes originally unaffected by it. Thus, changes such as in the form of mutations that can improve the activity of a transcription factor may mediate new target genes and consequently elicit rewiring. Here, we combined random mutagenesis in LkSef1 and iterative fluorescence-based sorting to select for mutations that can readily enhance its transcriptional activity. Using an LkSef1-enhanced GFP reporter system, gain-of-function mutants were selected, and point mutations were found to increase its transcriptional activity. Also, all mutations are concentrated outside the conserved domains suggesting undefined regions responsible for its activity. Once reconstituted in the genome, these high activity LkSef1 can potentially create novel networks and may ultimately provide mechanisms for transcriptional rewiring.
The activity of a transcription factor is easily evolvable