Table 1.

Different molecular principles guiding the interaction between transcription factors (TFs) of the STAT, IRF and Rel/NFκB families.

Mode of interaction	Example	References
TF1 regulates TF2 synthesis	•STAT1 regulates IRF1 and IRF8 synthesis •NFκB regulates IRF1 synthesis	(43) (44) (45)
Promoter occupancy of TF1 required for binding of TF2	•IRF8 required for NFκB/IRF3/7-dependent Ifnb enhanceosome assembly by LPS •IRF8 enhances IFNγ-induced gene transcription by STAT1 and IRF1 in myeloid cells	(46) (47) (48)
Promoter co-occupancy by TFs required for transcriptional activation	•ISGF3 and NFκB cooperate at iNOS and IL6 promoters •STAT1 and IRF1 cooperate in IFNγ-induced transcription	(49) (50) (51) (52)
Physical interaction of TFs	•IRF9 binds to STAT2 •IRF3 associates with RelA/p65 to function as coactivator at NFκB sites. Conversely, RelA/p65 functions as IRF3 coactivator at ISREs •U-STAT2 associates with RelA/p65 to induce IL6 transcription	(10) (37) (53) (54) (55)
TF competition for promoter binding (direct or indirect)	•STAT6 prevents NFκB binding at overlapping sites •STAT5 prevents STAT1 association at IRF8 promoter	(56) (57) (58)