Schematic representations of how BRD2 monomers could polymerise as long thin filaments. Key: N = N terminus, C = C terminus, F = Front Face, B = Back Face. A) The models are i) head-to-tail; ii) head-to-head and tail-to-tail; iii) front face to back face; iv) front face to front face and back face to back face. The favoured model for formation of very long filaments is the head-to-tail formation. B) Models of docked BRD2 monomers that are of the correct dimensions to form 3 nm diameter filaments that could extend over hundreds of nm. i) head-to-tail BRD2 monomers with their front faces all aligned on one side of the filament creating a bent polymer; ii) head-to-tail BRD2 monomers with their front faces on alternating sides of the filament creating a twisted polymer.