Correction to: Nature Biotechnology https://doi.org/10.1038/s41587-019-0315-8, published online 2 December 2019.

In the version of this article initially published, a negative sign was missing negating the exponent in each of the three instances of the equation for accessibility, appearing in Fig. 2c, Methods section “Billboard model of transcription” and Supplementary Fig. 9. The correct equations are, respectively, as follows:

$${\Omega} = \frac{1}{{1 + {\mathrm{e}}^{ - \left( {{\mathrm{DB}} \times P + c_p} \right)}}}$$
$${\Omega}_{\mathrm{p}} = \frac{1}{{1 + {\mathrm{e}}^{ - \left( {c_p + {\Sigma}^{TFx}{\mathrm{DB}}_{{\mathrm{px}}}P_x} \right)}}}$$
$${\Omega} = \frac{1}{{1 + e^{ - \left( {DB \cdot P + c_p} \right)}}}$$

The correct equation was used in all analyses. The errors have been corrected in the PDF and HTML versions of the article.