Fig. 1

Complex topology and dosage sensitivity. a Case of a trimer in which the green subunit is a bridge. Halving of the latter leads to halving trimer output. However, halving the amounts of the orange subunits can lead to as low as 25 % of trimer. Overexpression of the orange subunits can be inconsequential from the perspective of the trimer output but entails a futile cost, whereas overexpression of the green ones leads to a titration effect (formation of dimeric subcomplexes), which reduces trimer output. b When the orange  subunits can, for instance, preassemble, halving their amount translates into a proportional decrease of trimer and the increase of the green  ones does not alter the amount of trimer. This shows how the topology of the complex and not only its composition modulate dosage sensitivity