Stat (Signal transducer and activators of transcription) proteins mediate the biological activity of cytokines, including interleukins, interferons, erythropoietin, and growth factors. Ligand-receptor interaction activates constitutively-associated JAK family kinases as well as subsequent recruitment and activation of Stat proteins by tyrosine phosphorylation. Active Stat proteins then move to the nucleus to promote transcription of cytokine-inducible genes. Seven Stat proteins have been cloned, each of which is differentially expressed and/or activated in a cytokine-specific and cell type-specific manner. Stat1 and Stat2 are components of the ISGF3 (Interferon-Stimulated Gene Factor 3) complex, the primary transcription activator induced by interferon binding to a specific cell-surface receptor. Stat1 has two alternatively spliced isoforms, 91-kDa Stat1α and 84-kDa Stat1β; Stat1α has 38 additional C-terminal amino acids. In response to the binding of IFNα, IFNγ, EGF, PDGF, or CSF-1 to their respective receptors, the Stat1 subunits become tyrosine-phosphorylated at Y701, and the complex translocates to the nucleus. This forms an active complex that includes the DNA-binding p48 subunit, and is responsible for modulating interferon-stimulated genes (ISGs) transciption.
The 4a monoclonal antibody recognizes the phosphorylated Y701 in Stat1α and Stat1β.
The antibody was conjugated to BD Horizon™ Red 718, which has been developed exclusively by for BD Biosciences as a better alternative to Alexa Fluor™ 700. BD Horizon™ Red 718 can be excited by the red laser (628 – 640 nm) and, with an Em Max around 718 nm, it can be detected using a 730/45 nm filter. Due to similar excitation and emission properties, we do not recommend using R718 in combination with APC-R700 or Alexa Fluor™ 700.