Fig. 3

A mechanistic model of Gal4/Gal80/Gal3 interactions supports our hypothesis. a The model, when simultaneously fit to both the attenuation (i) and shuttling (ii) data, is able to adequately satisfy both scenarios. The same parameter sets were used in both (i) and (ii), with the only difference being that the levels of Gal4 and Gal80 are altered. The experimentally determined expression of lacZ due to Gal4 without Gal80 is shown in yellow (ctrl data), the simulation fit to these data is shown in cyan (ctrl sim). The expression of lacZ after the addition of Gal80 found through experiments is shown in magenta (target data), the simulation fits to these data are shown in black (target sim). b When Gal3 is added to the system, the model exhibits a similar phenotype as experimentally observed when the model is optimized for both attenuation and shuttling. The parameter sets here are the same as shown in (a). c When the model is fit only to the attenuation phenotype, the attenuation fit is better (i), but shuttling does not occur (ii). d With parameter sets that resulted from an attenuation-only optimization, as seen in (c), the presence of Gal3 does not result in a local increase in lacZ expression. The parameter sets here are the same as shown in (c)