Proposed model of granulocytic cell cycle arrest and differentiation by RARα. RARα directly activates C/EBPϵ. C/EBPϵ in turn is able to directly activate differentiation-associated genes, such as lactoferrin, that are required for functionally competent mature granulocytes. C/EBPϵ also directly mediates induction of Mad1, coupling cell cycle arrest pathways and differentiation induction by RARα.