Each of the GLI proteins can form a complex in the nucleus with CDC73, also known as Parafibromin, a component of the PAF complex (Mosimann et al, 2009). PAF1 is a conserved protein complex that affects aspects of RNA polymerase II transcription including histone modification, transcription elongation and RNA 3' end formation, among others. In humans, the PAF1 complex consists of CDC73, PAF1, LEO1, CTR9, RTF1 and WDR61 (reviewed in Tomson and Arndt, 2013). Knockdown of CDC73 in mammalian cell culture compromises GLI1- and GLI2-dependent transcriptional activation and has been shown to abrogate expression of endogenous targets in Drosophila. CDC73 interacts with the GLI proteins through the SUFU-interacting domain in region 1 of the N-terminal (Mosimann et al, 2009). Direct binding of a CDC73:GLI complex on an endogenous human target gene has not yet been demonstrated.