Arginine residues within the DNA binding domain of STAT3 promote intracellular shuttling and phosphorylation of STAT3.
Acetylation-dependent inactivation of STAT1 can be mimicked by the exchange of its lysine residues K410 and K413 to glutamine residues. STAT3 harbors non-acetylatable arginine moieties at the corresponding sites R414 and R417. It is unclear whether the mutation of these sites to glutamine residues antagonizes STAT3 activation. Here, we show that an arginine-glutamine-exchange at the STAT3 moieties R414 and R417 (R414Q and R417Q) reduces cytokine-dependent tyrosine phosphorylation of STAT3. This inhibitory effect can be partially rescued by phosphatase inhibition. In addition, the R414Q and R417Q mutations enhance the nuclear accumulation of unphosphorylated STAT3. STAT3 R414Q and STAT3 R417Q show a reduced response to cytokine stimulation emanating from the plasma membrane. Moreover, these STAT3 mutants have no direct inhibitory effect on the cytokine-induced activation of STAT1/STAT3-mediated gene expression. Since the mutations R414Q and R417Q reside within the STAT3 DNA binding domain (DBD), the STAT3 R414Q and R417Q mutants also lack intrinsic activity as transcription factors. Furthermore, in contrast to wild-type STAT3 they cannot compensate for a loss of STAT1 and they cannot promote STAT1/STAT3-dependent transcriptional activation. We further analyzed a STAT3 arginine-lysine-exchange mutant (R414K/R417K). This molecule mimics corresponding lysine residues found within the DBD of STAT1. Compared to wild-type STAT3, the STAT3 R414K/R417K mutant shows attenuated tyrosine phosphorylation and it is a less active transcription factor. In addition, STAT3 R414K/R417K is not activated by deacetylase inhibition. On the other hand, C-terminal acetylation of STAT3 is intact in STAT3 R414K/R417K. Our results suggest that the exchange of amino acid residues within the DBDs of STAT1/STAT3 affects their phosphorylation as well as their intracellular shuttling.
Center for Molecular Biomedicine (CMB), Dept. of Biochemistry, University of Jena, Germany.
Torsten
T
Ginter
Department of Toxicology, University Medical Center, Obere Zahlbacher Str. 67, 55131 Mainz, Germany.
Jörg
J
Fahrer
Center for Molecular Biomedicine (CMB), Dept. of Biochemistry, University of Jena, Germany.
Ulrike
U
Kröhnert
Department of Molecular and Cellular Oncology, University Hospital, Mainz, Germany.
Verena
V
Fetz
Center for Molecular Biomedicine (CMB), Dept. of Biochemistry, University of Jena, Germany.
Alessio
A
Garrone
Department of Molecular and Cellular Oncology, University Hospital, Mainz, Germany.
Roland H
RH
Stauber
University of Applied Sciences Jena, Department of Medical Engineering and Biotechnology, 07745 Jena, Germany.
Werner
W
Reichardt
Institute of Biochemistry and Molecular Biology, RWTH Aachen University, 52074 Aachen, Germany.
Gerhard
G
Müller-Newen
Center for Molecular Biomedicine (CMB), Dept. of Biochemistry, University of Jena, Germany.
Christian
C
Kosan
Center for Molecular Biomedicine (CMB), Dept. of Biochemistry, University of Jena, Germany.
Thorsten
T
Heinzel
Department of Toxicology, University Medical Center, Obere Zahlbacher Str. 67, 55131 Mainz, Germany. Electronic address: okraemer@uni-mainz.de.
Oliver H
OH
Krämer
D000107:Acetylation; D019943:Amino Acid Substitution; D001120:Arginine / Q000737:chemistry / Q000378:metabolism*; D045744:Cell Line, Tumor; D004247:DNA / Q000378:metabolism*; D006655:Histone Deacetylases / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D015533:Transcriptional Activation / Q000187:drug effects
D016898:Interferon-alpha; D015850:Interleukin-6; D050796:STAT3 Transcription Factor; D004247:DNA; D001120:Arginine; D006655:Histone Deacetylases
Acetylation; NES; NLS; Phosphorylation; STAT1; STAT3