Biomedical subjects

Steven E Jacobsen

Publications and source records attributed to Steven E Jacobsen.

3 recordsLinked to original sources

PubMed2026

Gene regulatory mechanisms downstream of DNA methylation.

Cytosine DNA methylation is a conserved epigenetic modification that regulates gene expression, represses transposable elements and maintains genome stability across diverse eukaryotes. Although major advances have uncovered the pathways involved in the establishment, maintenance and removal of DNA methylation, the downstream mechanisms by which this mark influences transcriptional programmes and shapes chromatin structure are less well understood. Here, we review how specialized reader proteins and transcription factors interpret DNA methylation to preserve methylation patterns, recruit effector complexes, regulate chromatin accessibility and interact with parallel epigenetic systems to mediate transcriptional silencing and activation across mammals and plants. We highlight that robust transcriptional and epigenetic states emerge from overlapping, layered and partially redundant DNA methylation-dependent mechanisms. Together, these insights provide a framework for understanding how DNA methylation shapes the epigenome to regulate development, differentiation and disease progression.

Journal Article↗

PubMed2026

Stepwise DNA-unwinding gates TnpB genome-editing activity.

TnpB is a compact RNA-guided endonuclease and an evolutionary ancestor of CRISPR-Cas12 that offers a promising platform for genome engineering. However, the genome-editing activity of TnpBs remains limited, and its underlying determinants are poorly understood. Here, we used biochemical and single-molecule assays to examine the DNA-unwinding mechanism of Youngiibacter multivorans TnpB (Ymu1 TnpB). DNA unwinding proceeds through a discrete, long-lived, partially unwound intermediate state before reaching a fully unwound open state. The open state forms inefficiently and collapses readily in the absence of negative supercoiling. An optimized variant, H4W-L304F-V305R (Ymu1-WFR), stabilizes formation of both the intermediate and open states, resulting in enhanced DNA cleavage in vitro and increased genome editing in plants. These findings identify the physical basis for the observed minimal activities of natural TnpBs, revealing how stabilizing specific unwinding states enables efficient DNA targeting.

Gene Editing↗

PubMed2026

Structure and evolution-guided design of minimal RNA-guided nucleases.

The design of RNA-guided nucleases with properties not limited by evolution can expand programmable genome-editing capabilities. However, generating diverse multidomain proteins with robust enzymatic properties remains challenging. Here, we use a protein design strategy that couples a structure-guided inverse-folding model with evolution-informed residue constraints to generate active, divergent variants of TnpB, a minimal CRISPR-Cas12-like nuclease, termed SynTnpBs. High-throughput screening of artificial intelligence-generated variants yielded editors that retained or exceeded wild-type activity in bacterial, plant, and human cells. Cryo-electron microscopy-based structure determination of the most divergent variant revealed stabilizing contacts in the RNA-DNA interfaces across conformations, demonstrating the design potential of this approach. Together, these results establish a strategy for creating non-natural RNA-guided nucleases and conformationally active nucleic acid binders, enlarging the designable protein space.

Humans↗