Anti-phospho-STAT1 (Tyr701) (Signal Transducer and Activator of Transcription 1), clone 3G272

In unstimulated cells, STAT proteins exist largely in the cytoplasm as latent transcription factors. In response to treatment of target cells with cytokines or in some cases growth factors, STATs undergo tyrosine phosphorylation, homo- or heterodimerization, nuclear translocation, and DNA binding which results in transcriptional activation of distinct target genes. Phosphorylation of a conserved tyrosine residue located near the carboxy-terminus of all STAT proteins is required for both dimerization and DNA binding. Tyrosine phosphorylation is therefore a useful marker for STAT activation. At least one and oftentimes several STAT proteins are activated in response to cytokines that utilize receptors from the cytokine receptor superfamily. Nevertheless, a striking specificity of specific STAT activation is seen in response to individual cytokines. Stimulation of responsive cells with IFNa/b induces the formation of a transcription complex termed ISGF3. This complex binds to the interferon-stimulated response element (ISRE), activating the transcription of responsive genes. The ISGF3 complex consists of tyrosine phosphorylated STAT1a, STAT1b (p84), STAT2 and p48, a 48kD DNA binding protein that is specific for the IFN-stimulated response element. Formation of this complex and its migration into the nucleus is dependent upon tyrosine phosphorylation of STAT1a/b and STAT2. Stimulation of cells with IFN-g results in tyrosine phosphorylation of STAT1a (p91), but not of STAT2. Phosphorylation of STAT1a results in its homodimerization and migration into the nucleus where it binds to the IFN-g activated site (GAS). The STAT1a and STAT1b isoforms arise by alternative splicing of a single gene. The only difference between the two proteins is that STAT1b lacks 38 carboxy-terminal amino acids. Contained within these 38 terminal amino acids of STAT1a is a critical serine residue (Ser727) whose phosphorylation is required for maximal IFN-g induced transcription. Applications: Suitable for use in ELISA, Western Blot, ChIP and Immunohistochemistry. Other applications not tested. Recommended Dilutions: ELISA: 0.1-1ug/ml, Western Blot: 0.5-2ug/ml , Immunohistochemistry (Paraffin): 1:10-1:100, ChIP: 5ug, Optimal dilutions to be determined by the researcher. Storage and Stability: May be stored at 4°C for short-term only. Aliquot to avoid repeated freezing and thawing. Store at -20°C. Aliquots are stable for 12 months after receipt. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap.