SP1 and keloid: PARP-1 is known to affect the transcriptional output of a Smad-sensitive promoter, which suggests that PARP-1 may play a more fundamental role in negatively regulating expression of TGF-β-responsive genes.28 Functionally, PARP-1 is known to regulate transcription factors, such as p53, Sp1, and NF-κB.29 In addition, p53,30 Sp1,31 and NF-kB32 is also well known as one of the factors involved in keloid pathogenesis.