TPA応答配列に結合する転写因子。Jun関連遺伝子、Fos関連遺伝子の産物からなるヘテロ二量体が主な成分となっている。
TPA応答配列
ホルボールエステル（12-O-テトラデカノイルホルボール13-アセテートなど）で細胞を刺激することで転写が活性化される遺伝子群の転写制御部位にある。TGACTCAを含むものが多い。AP1が結合し転写活性化に関与する。
Transcription factor AP-1
- Alternative name(s)
- Activator protein 1 (Short name=AP1) / Proto-oncogene c-Jun / V-jun avian sarcoma virus 17 oncogene homolog / p39
- Function
- Transcription factor that recognizes and binds to the enhancer heptamer motif 5'-TGA[CG]TCA-3'. Promotes activity of NR5A1 when phosphorylated by HIPK3 leading to increased steroidogenic gene expression upon cAMP signaling pathway stimulation. Ref.15 Ref.19
- Subunit structure
- Heterodimer with either FOS or BATF3 or ATF7. The ATF7/JUN heterodimer is essential for ATF7 transactivation activity. Interacts with DSIPI; the interaction inhibits the binding of active AP1 to its target DNA By similarity. Interacts with HIVEP3 and MYBBP1A By similarity. Interacts with SP1, SPIB and TCF20. Interacts with COPS5; the interaction leads indirectly to its phosphorylation. Component of the SMAD3/SMAD4/JUN/FOS/complex which forms at the AP1 promoter site. The SMAD3/SMAD4 heterodimer acts syngernistically with the JUN/FOS heterodimer to activate transcription in response to TGF-beta. Interacts (via its basic DNA binding and leucine zipper domains) with SMAD3 (via an N-terminal domain); the interaction is required for TGF-beta-mediated transactivation of the SMAD3/SMAD4/JUN/FOS/complex. Interacts with methylated RNF187. Binds to HIPK3.
- Subcellular location
- Nucleus.
- Post-translational modification
- Phosphorylated by CaMK4 and PRKDC; phosphorylation enhances the transcriptional activity. Phosphorylated by HIPK3. Phosphorylated by DYRK2 at Ser-243; this primes the protein for subsequent phosphorylation by GSK3B at Thr-239. Phosphorylated at Thr-239, Ser-243 and Ser-249 by GSK3B; phosphorylation reduces its ability to bind DNA. Phosphorylated by PAK2 at Thr-2, Thr-8, Thr-89, Thr-93 and Thr-286 thereby promoting JUN-mediated cell proliferation and transformation. Phosphorylated by PLK3 following hypoxia or UV irradiation, leading to increase DNA-binding activity. Ref.7 Ref.8 Ref.9 Ref.19 Ref.21 Ref.22 Ref.28 Ref.30
Acetylated at Lys-271 by EP300.
Proto-oncogene c-Fos
- Alternative name(s)
- Cellular oncogene fos / G0/G1 switch regulatory protein 7
- Function
- Nuclear phosphoprotein which forms a tight but non-covalently linked complex with the JUN/AP-1 transcription factor. In the heterodimer, FOS and JUN/AP-1 basic regions each seems to interact with symmetrical DNA half sites. On TGF-beta activation, forms a multimeric SMAD3/SMAD4/JUN/FOS complex at the AP1/SMAD-binding site to regulate TGF-beta-mediated signaling. Has a critical function in regulating the development of cells destined to form and maintain the skeleton. It is thought to have an important role in signal transduction, cell proliferation and differentiation. In growing cells, activates phospholipid synthesis, possibly by activating CDS1 and PI4K2A. This activity requires Tyr-dephosphorylation and association with the endoplasmic reticulum.
- Subunit structure
- Heterodimer; with JUN. Interacts with MAFB. Component of the SMAD3/SMAD4/JUN/FOS complex required for syngernistic TGF-beta-mediated transcription at the AP1 promoter site. Interacts with SMAD3; the interaction is weak even on TGF-beta activation. Interacts with MAFB. Interacts with DSIPI; this interaction inhibits the binding of active AP1 to its target DNA. Interacts with CDS1 and PI4K2A By similarity.
- Subcellular location
- Nucleus. Endoplasmic reticulum. Cytoplasm › cytosol. Note: In quiescent cells, present in very small amounts in the cytosol. Following induction of cell growth, first localizes to the endoplasmic reticulum and only later to the nucleus. Localization at the endoplasmic reticulum requires dephosphorylation at Tyr-10 and Tyr-30.
- Developmental stage
- Expressed at very low levels in quiescent cells. When cells are stimulated to re-enter growth, they undergo 2 waves of expression, the first one peaks 7.5 minutes following FBS induction. At this stage, the protein is localized endoplasmic reticulum. The second wave of expression occurs at about 20 minutes after induction and peaks at 1 hour. At this stage, the protein becomes nuclear. Ref.15
- Post-translational modification
- Phosphorylated in the C-terminal upon stimulation by nerve growth factor (NGF) and epidermal growth factor (EGF). Phosphorylated, in vitro, by MAPK and RSK1. Phosphorylation on both Ser-362 and Ser-374 by MAPK1/2 and RSK1/2 leads to protein stabilization with phosphorylation on Ser-374 being the major site for protein stabilization on NGF stimulation. Phosphorylation on Ser-362 and Ser-374 primes further phosphorylations on Thr-325 and Thr-331 through promoting docking of MAPK to the DEF domain. Phosphorylation on Thr-232, induced by HA-RAS, activates the transcriptional activity and antagonizes sumoylation. Phosphorylation on Ser-362 by RSK2 in osteoblasts contributes to osteoblast transformation By similarity. Ref.9 Ref.11 Ref.15 Ref.17
Constitutively sumoylated with SUMO1, SUMO2 and SUMO3. Desumoylated by SENP2. Sumoylation requires heterodimerization with JUN and is enhanced by mitogen stimulation. Sumoylation inhibits the AP-1 transcriptional activity and is, itself, inhibited by Ras-activated phosphorylation on Thr-232. Ref.12 Ref.14
In quiescent cells, the small amount of FOS present is phosphorylated at Tyr-10 and Tyr-30 by SRC. This Tyr-phosphorylated form is cytosolic. In growing cells, dephosphorylated by PTPN2. Dephosphorylation leads to the association with endoplasmic reticulum membranes and activation of phospholipid synthesis.
