Fig. 2: MEK1 regions were defined by drop-out screen and mapped to different protein domains.

a PAR/Cas9-D14 LFC values were plotted to the MEK1 protein primary sequence. All sgRNAs with LFC values less than -4.35 (dashed line) are labelled as ‘sg + targeting residues’ and indicated by arrows. Dots are coloured according to MEK1 domains. A-loop: activation loop, K1-K4: core kinase domain 1-4, P-rich loop: proline-rich loop. Data points represent mean of two replicates. b Overview of the MEK1 regions targeted by the most depleted sgRNAs, mapped to the protein crystal structure. MEK1 residues are colour-coded by sgRNA bins in a heatmap style. Colour codes of the sgRNA bins are indicated below the structures. Molecule in green: ADP. PDB code: 3EQI. c A close-up view of the regions around the active site (ATP binding pocket). The molecule in the pocket is an ATP analogue, AMP-PNP. d A close-up view of the regions at the MEK1-BRAF PPI interface. BRAF protein ribbon is coloured in yellow. A hydrogen bond between MEK1 V224 and BRAF G615 is indicated as a dotted green line. e A close-up view of the regions at the MEK1 mutation hotspots. Known MEK1 oncogenic mutations at each of the regions are indicated in brackets. c–e PDB code, 6V2W. MEK1 protein ribbon is coloured in light green. MEK1 domains are labelled and indicated with arrows in grey. Key residues are displayed as ball-and-sticks, labelled, and indicated by arrows in the same colours as the highly depleted region.