Transcriptional repression of MMP-1 by p21SNFT and reduced in vitro invasiveness of hepatocarcinoma cells

p21(SNFT) (21 kDa small nuclear factor isolated from T cells) is a human basic leucine zipper transcription factor that can repress AP-1-mediated transcription. We show here that overexpression of p21(SNFT) in HepG2 cells leads to repression of matrix metalloproteinase-1 by 70-80%. p21(SNFT) interacted with Jun at the matrix metalloproteinase-1 promoter -88 Ets/AP-1 enhancer element, where Jun is known to activate transcription via interaction with Fos and Ets proteins. When p21(SNFT)/Jun dimers bound the element in the presence of Ets, DNA was protected differently than when Fos was paired with Jun. The data suggest a difference in overall conformation between p21(SNFT)-containing and Fos-containing complexes that may be involved in the repression of matrix metalloproteinase-1 by p21(SNFT). Overexpression of p21(SNFT) led to a reduction in invasiveness of HepG2 cells through type I collagen and reconstituted basement membrane, an effect similar to that obtained via direct immunodepletion of matrix metalloproteinase-1. The results indicate that the mechanism of repression of matrix metalloproteinase-1 by p21(SNFT) may be exploited in inhibiting pathological matrix remodeling during cancer progression in vivo.