A Modular and Customizable CRISPR/Cas Toolkit for Epigenome Editing of <i>Cis</i> ‐regulatory Modules

Epigenome and cis-regulome, comprising cis-regulatory elements (CREs) and modules (CRMs), jointly define the architecture of gene regulation. However, the causal mechanisms by which epigenetic marks influence CRM function remain elusive. To address this, modular epigenome editing frameworks, exemplified by dead Cas9-coupled DNA demethylation (dCd) and DNA methylation (dCm) platforms, are developed for programmable dissection and engineering of CRM activity. The dCd system modulates methylation levels and transcriptional output at CRMs in situ or ex situ, in accordance with CRM-specific methylation responsiveness, and alters co-transcriptional RNA processing to yield predictable phenotypic outcomes in plants. These findings underscore the reliability of targeted DNA demethylation. In parallel, the dCm system reconstitutes methylation-dependent and -sensitive CRMs of diverse origins in Saccharomyces cerevisiae, a species devoid of native DNA methylation, enabling causal dissection of epigenetic regulation and revealing cross-species portability. This system further uncovers crosstalk between DNA methylation and chromatin modifications, and enables logic-gated control of endogenous genes through CRM engineering. Incorporation of optogenetic and temperature-sensitive anti-CRISPR inhibitors confers tunable, reversible regulation, proposing dCm as a foundation for input-responsive synthetic epigenome editors. Together, these frameworks provide a versatile platform to decode and reprogram cis-regulatory epigenetic logic, with broad applications in trait design and synthetic biology.