Transcription-dependent swelling of a transplanted chromosome in an artificial cell

Abstract

Transplanting chromosomes from living to artificial cells would impact our understanding of chromosome organization and DNA transactions, with implications for autonomous biological systems. Here, we transplanted Escherichia coli chromosomes into artificial cells, enabling real-time labeling, manipulation, and steady-state gene expression down to the single-molecule limit. Chromosomes stripped of native proteins transitioned from a swollen to compacted state induced by transcription inhibition, in contrast to protein-bound chromosomes retaining an organization with blobs. In a cell-free expression reaction, RNA polymerases were uniformly distributed along the entire chromosome and rapidly detached, consistent with a global transcriptional activity. We used tailored surfaces to capture and count 20 nascent proteins per hour from a single gene on the chromosome. We mapped stably bound condensins to the blobs, supporting a model where swelling by transcription is counterbalanced by condensin-mediated compaction. Our data suggest transplanted chromosomes as active gels organized by molecular machines.