Signal Transducer and Activator of Transcription 3

• Species; Human
• Expression Host: E. coli
• Tag: His-tag
• Purity: 90%
• Molecular Weight: 90.0 kDa..
• Gene Accession Number: NM_003150.

Purification and Quality Control

The His-tag recombinant protein is purified by affinity chromatography in combination with FPLC columns. The purified STAT3 is greater than 90% homogeneous based on SDS-PAGE analysis.

Unit Definition (Activity)

1 unit equals 1 nanogram of purified protein. 1 unit is sufficient for a gel mobility shift assay in a 20 µl reaction; 100 units are sufficient for protein-protein interaction assays.

Applications

STAT3 can be used for 1) in vitro transcription; 2) gel mobility shift assay and 3) for protein-protein interactions assay.

Formulation and Storage

The protein is in 20mM Tris-HCl pH7.9,100mM NaCl, 0.2mM EDTA, 1mM DTT and 20% glycerol. Stored at -70°C before use. Avoid repeated freeze thaw cycles.

SYNONYM

APRF; FLJ20882; HIES and MGC16063.

Protein Sequence

MAQWNQLQQL DTRYLEQLHQ LYSDSFPMEL RQFLAPWIES QDWAYAASKE SHATLVFHNL
LGEIDQQYSR FLQESNVLYQ HNLRRIKQFL QSRYLEKPME IARIVARCLW EESRLLQTAA
TAAQQGGQAN HPTAAVVTEK QQMLEQHLQD VRKRVQDLEQ KMKVVENLQD DFDFNYKTLK
SQGDMQDLNG NNQSVTRQKM QQLEQMLTAL DQMRRSIVSE LAGLLSAMEY VQKTLTDEEL
ADWKRRQQIA CIGGPPNICL DRLENWITSL AESQLQTRQQ IKKLEELQQK VSYKGDPIVQ
HRPMLEERIV ELFRNLMKSA FVVERQPCMP MHPDRPLVIK TGVQFTTKVR LLVKFPELNY
QLKIKVCIDK DSGDVAALRG SRKFNILGTN TKVMNMEESN NGSLSAEFKH LTLREQRCGN
GGRANCDASL IVTEELHLIT FETEVYHQGL KIDLETHSLP VVVISNICQM PNAWASILWY
NMLTNNPKNV NFFTKPPIGT WDQVAEVLSW QFSSTTKRGL SIEQLTTLAE KLLGPGVNYS
GCQITWAKFC KENMAGKGFS FWVWLDNIID LVKKYILALW NEGYIMGFIS KERERAILST
KPPGTFLLRF SESSKEGGVT FTWVEKDISG KTQIQSVEPY TKQQLNNMSF AEIIMGYKIM
DATNILVSPL VYLYPDIPKE EAFGKYCRPE SQEHPEADPG SAAPYLKTKF ICVTPTTCSN
TIDLPMSPRT LDSLMQFGNN GEGAEPSAGG QFESLTFDME LTSECATSPM

Background

Signal transducer and activator of transcription (STAT) proteins are a family of latent cytoplasmic transcription factors involved in cytokine, hormone, and growth factor signal transduction (1). Seven members of the STAT family of transcription factors have been identified in mammalian cells: STAT1, STAT2, STAT3, STAT4, STAT5a, STAT5b, and STAT6. STAT proteins mediate broadly diverse biological processes, including cell growth, differentiation, apoptosis, fetal development, transformation, inflammation, and immune response (reviewed in 2, 3). Receptor-recruited STATs are phosphorylated on a single tyrosine residue in the carboxy terminal portion. The modified STATs are released from the cytoplasmic region of the receptor subunits to form homodimers or heterodimers through reciprocal interaction between the phosphotyrosine of one STAT and the SH2 domain of another (4-6). Following dimerization, STATs rapidly translocate to the nucleus and interact with specific regulatory elements to induce target gene transcription (7, 8). Unlike all other members of the STAT gene family, ablation of STAT3 leads to embryonic lethality and it has been suggested that this protein might represent a primordial STAT protein (9, 10).
It evokes a number of distinct responses in different cells, including induction of an acute-phase response in hepatoma cells, stimulation of proliferation in B lymphocytes, activation of terminal differentiation and growth arrest in monocytes, and maintenance of the pluripotency of embryonic stem cells. Dysregulation of STAT signaling pathways, particularly STAT3 and STAT5, has been demonstrated to contribute to malignant cellular transformation (11, 12). Constitutive activation of STAT1, STAT3, and STAT5 is associated with malignant transformation induced by various oncoproteins. Src kinase-mediated activation of STAT3 has been shown to be essential in prostate and ovarian carcinomas (13). In head and neck cancers, constitutive STAT3 activity with up-regulated epidermal growth factor receptor (EGFR) signaling plays an important role in malignant proliferation (14). Altering the c-terminal domain of STAT3 induces constitutive activation and provides further evidence that STAT3 activation may be oncogenic by itself and is not just a consequence of tyrosine phosphorylation (15). Therefore, STAT3 may be a key player in the pathogenesis of diverse human cancers which makes this molecule a prime target for novel therapies.

Image of SDS-PAGE /Western-blot