Fig. 8. A model for regulation of MMP-9 expression by 3ß1. MMP-9 gene transcription can be induced by Ras/MEK/ERK signaling in response to growth factors, cytokines, or oncogenic Ras. Our data reveal a novel mechanism wherein 3ß1 is required for stabilization of MMP-9 mRNA, leading to the accumulation of MMP-9 transcripts and subsequent production of MMP-9 protein in response to ERK-mediated transcriptional induction. In the absence of 3ß1, transcriptional induction by Ras/MEK/ERK does not lead to substantial accumulation of MMP-9 transcript and increased MMP-9 protein owing to the destabilization and rapid decay of MMP-9 mRNA. The 3 and ß1 integrin subunits are indicated.