# Engineering Light-Responsive Transcription Factors via Strategic Masking of Post-translational Modification Residues

## TL;DR

Scientists created light-sensitive transcription factors by masking key residues, allowing precise control of DNA binding with light.

## Contribution

A novel method to engineer light-responsive transcription factors using strategic masking of modification residues.

## Key findings

- Caged Max variant showed reduced DNA-binding activity when residues were masked.
- DNA-binding activity was rapidly restored upon light-induced unmasking of Lys31/57.
- The method enables on-demand activation of transcription factors within minutes using photolysis.

## Abstract

The development of
synthetic transcription factors (TFs)
that generate
functional outputs in response to specific stimuli holds significant
promise for modulating key cellular processes in both basic research
and biomedical applications. Here, we rationally designed synthetic
TFs bearing reversible modifications that mimic post-translational
modifications regulatory mechanisms. By combining native chemical
ligation (NCL) with palladium-mediated C–S cross-coupling,
we synthesized a caged Max variant in which key residues (e.g., Lys31/57)
were masked with o-nitroveratryloxycarbonyl groups. While the preparation
of photoreactive proteins is generally incompatible with traditional
NCL–desulfurization approaches, our strategy highlights the
power of integrating total synthesis with late-stage transformations
to access novel photoreactive proteins. Remarkably, whereas the engineered
caged Max displayed a pronounced reduction in DNA-binding activity,
potent binding to the enhancer box was rapidly restored upon site-selective
unmasking of Lys31/57. The caged Max can be efficiently activated
on-demand within minutes by simple in situ photolysis, enabling precise
modulation of its DNA-binding activity. Our approach provides an effective
means for producing and activating TF proteins, paving the way for
light-responsive TF analogs with on-demand control across diverse
applications.