Transcriptional synergy mediated by SAF-1 and AP-1: critical role of N-terminal polyalanine and two zinc finger domains of SAF-1.
Previously we determined that inflammation responsive transcription factors AP-1 and SAF-1 synergistically regulate transcriptional induction of the MMP-1 gene. The present study investigated the underlying molecular mechanism of cooperativity between these two different groups of transcription factors. We present evidence that knockdown of SAF-1 by small interfering RNAs inhibits AP-1-mediated increase of human MMP-1 expression. The two key members of the AP-1 family of proteins, c-Fos and c-Jun, and SAF-1 form a ternary protein complex, which has markedly higher DNA binding activity than either a SAF-1 homodimer or a c-Fos/c-Jun heterodimer. The increased DNA binding activity of the ternary complex is translated into a striking enhancement of their transcriptional activity by which synergistic transcriptional induction of MMP-1 expression is achieved. The SAF-1.c-Fos.c-Jun ternary complex efficiently promotes transcription from both SAF-1 and AP-1 sites of human MMP-1 promoter. The physical interaction between SAF-1 and AP-1 was demonstrated both in vitro by Far-Western and antibody pulldown assays with recombinant proteins and in vivo by chromatin immunoprecipitation (ChIP), re-ChIP, and co-immunoprecipitation analyses. Two distinct but adjacent domains in SAF-1 are involved in protein-protein contact with c-Fos and c-Jun; one domain resides within two N-terminal polyalanine tracts, and the other is present within the first two zinc finger motifs. Together these findings delineate the mechanism of synergy and the essential role of SAF-1 and AP-1 in up-regulating human MMP-1 expression under various inflammatory conditions.
Kumar
Deepak
D
Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri 65211, USA.
Ray
Alpana
A
Ray
Bimal K
BK
D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004790:Enzyme Induction / Q000502:physiology; D006801:Humans; D020781:Matrix Metalloproteinase 1 / Q000096:biosynthesis*; D046912:Multiprotein Complexes / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D020836:Protein Structure, Quaternary / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D020218:Response Elements / Q000502:physiology; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*; D016335:Zinc Fingers / Q000502:physiology
D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; D010455:Peptides; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D014157:Transcription Factors; C076035:c-MYC-associated zinc finger protein; C019529:polyalanine; C522360:MMP1 protein, human; D020781:Matrix Metalloproteinase 1