Total Synthesis of Site-Specifically Modified bHLHLz Transcription Factors Reveals Insights into the Regulatory Role of Posttranslational Modifications in the Myc–Max–Mad Network
- 1School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences
- 2Tel Aviv University
Abstract
The Myc–Max–Mad bHLHLz transcription factor (TF) network regulates the expression of ~15% of the human genome, and its dysregulation is implicated in nearly 70% of human cancers. Although its activity is primarily governed by competition for dimerization partners and occupancy of shared DNA target sequences, the molecular mechanisms controlling oligomerization and DNA binding remain elusive. Here, we employed total protein synthesis and combinatorial assembly to define how posttranslational modification (PTM) patterns regulate the Myc–Max–Mad TF network. Using native chemical ligation, we prepared a library of site-specifically modified Myc, Mnt, Mad, and phosphorylated or acetylated Max analogs. Remarkably, the isolation of homogeneous TFs enabled the combinatorial generation of all 24 heterodimeric complexes, allowing systematic analysis of dimerization and DNA-binding activity across the network. Our findings provide direct evidence that although Max phosphorylation and acetylation do not significantly affect its oligomerization with the Myc transcriptional activator, these modifications enhance its dimerization with the transcriptional repressors Mnt and Mad. Moreover, we found that Max-PTMs modulate DNA-binding activity by both specific PTM patterns and combinations, as well as the identity of the TF partner. Together, these findings demonstrate that PTM-dependent modulation of DNA-binding activity within the Myc–Max–Mad network constitutes a key regulatory layer governing gene expression.
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BibTeX
@misc{nithun2026total,
title = {{Total Synthesis of Site-Specifically Modified bHLHLz Transcription Factors Reveals Insights into the Regulatory Role of Posttranslational Modifications in the Myc–Max–Mad Network}},
author = {Raj V. Nithun and Muhammad Jbara},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010142/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010142/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Total Synthesis of Site-Specifically Modified bHLHLz Transcription Factors Reveals Insights into the Regulatory Role of Posttranslational Modifications in the Myc–Max–Mad Network
AU - Raj V. Nithun
AU - Muhammad Jbara
PY - 2026
DA - 2026/10/09
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010142/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010142/v1
AB - The Myc–Max–Mad bHLHLz transcription factor (TF) network regulates the expression of ~15% of the human genome, and its dysregulation is implicated in nearly 70% of human cancers. Although its activity is primarily governed by competition for dimerization partners and occupancy of shared DNA target sequences, the molecular mechanisms controlling oligomerization and DNA binding remain elusive. Here, we employed total protein synthesis and combinatorial assembly to define how posttranslational modification (PTM) patterns regulate the Myc–Max–Mad TF network. Using native chemical ligation, we prepared a library of site-specifically modified Myc, Mnt, Mad, and phosphorylated or acetylated Max analogs. Remarkably, the isolation of homogeneous TFs enabled the combinatorial generation of all 24 heterodimeric complexes, allowing systematic analysis of dimerization and DNA-binding activity across the network. Our findings provide direct evidence that although Max phosphorylation and acetylation do not significantly affect its oligomerization with the Myc transcriptional activator, these modifications enhance its dimerization with the transcriptional repressors Mnt and Mad. Moreover, we found that Max-PTMs modulate DNA-binding activity by both specific PTM patterns and combinations, as well as the identity of the TF partner. Together, these findings demonstrate that PTM-dependent modulation of DNA-binding activity within the Myc–Max–Mad network constitutes a key regulatory layer governing gene expression.
ER -