[Paper Review] Long-term evolution of regulatory DNA sequences. Part 2: Theory and future challenges

Elia Mascolo, Réka Borbély+4 more|arXiv (Cornell University)|Jan 29, 2026

Genomics and Chromatin Dynamics0 citations

TL;DR

This invited review surveys how evolutionary concepts apply to the long-term evolution of cis-regulatory elements, discusses a potential unifying theory, and outlines future challenges.

ABSTRACT

Promoters and enhancers are cis-regulatory elements (CREs), DNA sequences that bind transcription factor (TF) proteins to up- or down-regulate target genes. Decades-long efforts yielded TF-DNA interaction models that predict how strongly an individual TF binds arbitrary DNA sequences and how individual binding events on the CRE combine to affect gene expression. These insights can be synthesized into a global, biophysically-realistic, and quantitative genotype-phenotype (GP) map for gene regulation, a "holy grail" for the application of evolutionary theory. A global map provides a rare opportunity to simulate long-term evolution of regulatory sequences and pose several fundamental questions: How long does it take to evolve CREs de novo? How many non-trivial regulatory functions exist in sequence space? How connected are they? For which regulatory architecture is CRE evolution most rapid and evolvable? In this article, the second of a two-part series, we review the application of evolutionary concepts - epistasis, robustness, evolvability, tunability, plasticity, and bet-hedging - to the evolution of gene regulatory sequences. We then evaluate the potential for a unifying theory for the evolution of regulatory sequences, and identify key open challenges.

Motivation & Objective

• Motivate study of CRE evolution by connecting TF-DNA interaction models to evolutionary theory.
• Survey concepts such as epistasis, robustness, evolvability, tunability, plasticity, and bet-hedging as they apply to CREs.
• Evaluate the prospects for a global, biophysically realistic genotype-phenotype map for gene regulation.
• Identify open questions and challenges needed to formulate a unifying theory for CRE evolution.

Proposed method

• Synthesize existing evolutionary theory concepts (epistasis, robustness, evolvability, tunability, plasticity, bet-hedging) as they relate to CRE evolution.
• Assess the potential for a global, biophysically realistic GP map for gene regulation as a framework for long-term evolution.
• Review the current state of TF-DNA interaction models and their integration into evolutionary questions about CREs.
• Identify conceptual and methodological challenges in unifying CRE evolutionary theory.

Experimental results

Research questions

• RQ1 How long does it take for regulatory elements to evolve de novo under evolutionary forces?
• RQ2 How many non-trivial regulatory functions exist in the sequence space of CREs, and how are they connected?
• RQ3 For which regulatory architectures is CRE evolution most rapid and evolvable?
• RQ4 What conditions are required for a unifying, quantitative theory of regulatory sequence evolution to emerge?

Key findings

• The paper reviews the application of evolutionary concepts to CRE evolution.
• It evaluates the potential for a unifying theory of CRE evolution.
• It identifies key open challenges in developing a quantitative GP map for gene regulation.