Complex sentence: IKK-α carries out this regulatory role by acting as a cofactor in the TGF-β/Smad2/3 signalling pathway which in turn controls the exiting of keratinocytes from the cell cycle.
Split into simpler sentences: IKK-α is a cofactor in the TGF-β/Smad2/3 signalling pathway. This pathway controls the exiting of keratinocytes from the cell cycle.