The interior of a cell is a chaotic, turbulent place dominated by random, thermally driven collisions.  Inside this tempest, the internal structures of a cell must do their delicate work.  The creation of a single strand of mRNA, essential for creating the proteins that make cells run, requires the meticulous assembly of long sequences of adenine, cytosine, guanine, and uracil.  Yet despite the ever present internal squall and the exacting nature of the work, these cellular processes have surprisingly low error rates.  The chance of a transcription error inside e. coli bacteria, for example, has been observed to be about 1 in 10,000.      Explaining how such high accuracy is achieved under such adverse conditions is an enduring challenge for biology.  This grant funds a series of experiments designed by Rockefeller University’s Gregory Alushin, Amy Shyer, and Shixin Liu that explore one promising explanation: mechanical force. Alushin, Shyer, and Liu will use grant funds to field two research projects that use emerging technologies, such as high-resolution imaging and tools that apply and measure nanoscale forces, to explore the role played by mechanical force in two areas of biology. In the first, Alushin, Shyer, and Liu will work at the nanoscale to test the hypothesis that force influences the fidelity of the molecular machine that executes the primary step in gene expression, the copying of genetic information from DNA to RNA (transcription). This multiprotein machine is called RNA polymerase (RNAP) and the project team hypothesizes that force can cause RNAP to adopt structures that favor error correction during transcription. To test this, the team will exert forces on RNAP and measure the resulting error rates and structures. In the second project, the team will examine the role of force in morphogenesis, the development of heterogeneity in an initially uniform collection of cells (e.g., tissue) that underlies organ development. The team will use force manipulation and imaging to directly probe how force propagates across tissue-scale lengths while also mapping how force drives the molecular-scale rearrangements that launch gene expression. Here the principal investigators hypothesize that force propagates at a speed that exceeds what’s possible in models of chemical-signal propagation.