Pioneer factors can function passively, by acting as a bookmark for the cell to recruit other transcription factors to specific genes in condensed chromatin.  This can be important for priming the cell for a rapid response as the enhancer is already bound by a pioneer transcription factor giving it a head start towards assembling the transcription preinitiation complex.  Hormone responses are often quickly induced in the cell using this priming method such as with the estrogen receptor.  Another form of priming is when an enhancer is simultaneously bound by activating and repressing pioneer factors.  This balance can be tipped by dissociation of one of the factors.  In hepatic cell differentiation the activating pioneer factor FOXA1 recruits a repressor, grg3, that prevents transcription until the repressor is down-regulated later on in the differentiation process.
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In a direct role pioneer factors can bind an enhancer and recruit activation complex that will modify the chromatin directly.  The change in the chromatin changes the affinity, decreasing the affinity of the pioneer factor such that it is replaced by a transcription factor that has a higher affinity.  This is a mechanism for the cell to switch a gene on was observed with glucocorticoid receptor recruiting modification factors that then modify the site to bind activated estrogen receptor which was coined as a “bait and switch” mechanism.