Amino acid residues required for physical and cooperative transcriptional interaction of STAT3 and AP-1 proteins c-Jun and c-Fos.
Cooperation between STAT3 and c-Jun in driving transcription during transfection of reporter constructs is well established, and both proteins are present on some interleukin-6 (IL-6) STAT3-dependent promoters on chromosomal loci. We report that small interfering RNA knockdown of c-Jun or c-Fos diminishes IL-6 induction of some but not all STAT3-dependent mRNAs. Specific contact sites in STAT3 responsible for interaction of a domain of STAT3 with c-Jun were known. Here we show that the B-zip domain of c-Jun interacts with STAT3 and that c-Jun mutation R261A or R261D near but not in the DNA binding domain blocks in vitro STAT3-c-Jun interaction and decreases costimulation of transcription in transfection assays. Cooperative binding to DNA of tyrosine-phosphorylated STAT3 and both wild-type and R261A mutant c-Jun was observed. Even c-Jun mutant R261D, which on its own did not bind DNA, bound DNA weakly in the presence of STAT3. We conclude that a functional interaction between STAT3 and c-Jun while bound to chromosomal DNA elements exists and is necessary for driving transcription on at least some STAT3 target genes. Identifying such required interactive protein interfaces should be a stimulus to search for compounds that could ultimately inhibit the activity of STAT3 in tumors dependent on persistently active STAT3.
Ginsberg
Michael
M
Laboratory of Molecular Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Czeko
Elmar
E
Müller
Patrick
P
Ren
Zhiyong
Z
Chen
Xiaomin
X
Darnell
James E
JE
D000595:Amino Acid Sequence; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D045744:Cell Line, Tumor; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology; D008113:Liver Neoplasms / Q000473:pathology; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D019947:Receptors, Interleukin-6 / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D015850:Interleukin-6; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D019947:Receptors, Interleukin-6; D011994:Recombinant Proteins; D050796:STAT3 Transcription Factor; D018808:Transcription Factor AP-1; D005982:Glutathione Transferase