p16 inhibits matrix metalloproteinase-2 expression via suppression of Sp1-mediated gene transcription

✍ Scribed by Chie-Hong Wang; Hui-Chiu Chang; Wen-Chun Hung

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 243 KB
• Volume: 208
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.20660

✦ Synopsis

Abstract

Previous studies demonstrate that p16, a cyclin‐dependent kinase inhibitor and a tumor suppressor, may inhibit matrix metalloproteinase‐2 (MMP‐2) expression in human cancer cells to suppress tumor invasion and metastasis. However, the detailed mechanism is still unclear. Our results show that p16 inhibits MMP‐2 expression via transcriptional repression. Promoter deletion and mutation analysis indicates that p16 acts through the Sp1 transcription factor‐binding site located between −72 and −64 bp region from the transcriptional start site of the human MMP‐2 promoter to repress gene expression. DNA affinity precipitation assay (DAPA) and chromatin immuno‐precipitation (CHIP) assay demonstrate that Sp1 proteins constitutively bind to this consensus sequence in vitro and in vivo. p16 attenuates Sp1 binding to the MMP‐2 promoter to suppress gene transcription and overexpression of Sp1 may counteract p16‐induced downregulation of MMP‐2. CyclinA/CDK complex may directly phosphorylate Sp1 and enhance its DNA‐binding activity. Thus, we investigated the effect of p16 on the interaction between cyclin A and Sp1. Our results indicate that p16 induces downregulation of cyclin A and CDK2, reduces the interaction between cyclin A and Sp1, and attenuates phosphorylation of Sp1. Ectoexpression of cyclin A counteracts p16‐mdeiated inhibition of DNA binding of Sp1 and activates MMP‐2 promoter activity and mRNA expression. Collectively, our results suggest that p16 suppresses MMP‐2 by blocking Sp1‐mediated gene transcription. J. Cell. Physiol. © 2006 Wiley‐Liss, Inc.