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In molecular biology, a transcription factor is a protein that binds DNA at a specific promoter or enhancer region or site, where it regulates transcription. Transcription factors can be selectively activated or deactivated by other proteins, often as the final step in signal transduction.

Classes[edit | edit source]

There are three classes of transcription factors:

Motifs found in transcription factors[edit | edit source]

Examples of transcription factors[edit | edit source]

STAT[edit | edit source]

The Signal Transducers and Activator of Transcription (STAT) protein regulate many aspects of cell growth, survival and differentiation. The transcription factors of this family are activated by the Janus Kinase JAK and dysregulation of this pathway is frequently observed in primary tumors and leads to increased angiogenesis and enhanced survival of tumors. Knockout studies have provided evidence that STAT proteins are involved in the development and function of the immune system and play a role in maintaining immune tolerance and tumor surveillance.

Function of STAT proteins[edit | edit source]

STAT proteins were originally described as latent cytoplasmic transcription factors that require phosphorylation for nuclear retention. The unphosphorylated STAT proteins shuttle between the cytosol and the nucleus waiting for its activation signal. Once the activated transcription factors reach the nucleus, they bind to a consensus DNA-recognition motif called gamma activated sites (GAS) in the promoter region of cytokine inducible genes and activate transcription of these genes.

Activation of STAT proteins[edit | edit source]

Extracellular binding of Cytokines induces activation of the intracellular Janus kinase that phosphorylates a specific tyrosine residue in the STAT protein which promotes the dimerization of STAT monomers via their SH2 domain. The phosphorylated dimer is then actively transported in the nucleus via importin a/b and RanGDP complex. Once inside the nucleus the active STAT dimer binds to cytokine inducible promoter regions of genes containing gamma activated site (GAS) motif and activate transcription of this proteins. The STAT protein can be dephosphorylated by nuclear phosphatasess which leads to inactivation of STAT and the transcription factor becomes transported out of the nucleus by exportin crm1/

See also[edit | edit source]

External links[edit | edit source]

Entries of transcription factors at genetic databases[edit | edit source]

de:Transkriptionsfaktor es:Factor de transcripción he:גורם שעתוק fi:Transkriptiofaktori

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