Transcription Factors

Transcription factors are proteins involved in the process of converting DNA to RNA. They modulate the rate of gene transcription and are involved in protein synthesis. These proteins have the unique ability to bind DNA-regulatory sequences usually found in 5’-upstream regions of the targeted genes. Depending on the transcription factor, the binding site can be a promotor or regulatory sequence which can either stimulate or suppress transcription of the related gene. As such, the activation of transcription factors may result in increased or decreased gene transcription. A large portion of the human genome codes for these proteins. There are several families of transcription factors. Members of each family may share similar structural characteristics. These families include

• helix-turn-helix (e.g. Oct-1)
• helix-loop-helix (e.g. E2A)
• zinc finger (e.g. glucocorticoid receptors, GATA proteins)
• basic protein-leucine zipper [cyclic AMP response element-binding factor (CREB), activator protein-1 (AP-1)]
• β-sheet motifs [e.g. nuclear factor-κB (NF-κB)

Transcription factors are involved in many biological processes. Many transcriptions can be found in several cell types such as AP-1 and NF-κB. They play a general role in the regulation of inflammatory genes. Other transcription factors that are more cell-specific are involved in determining the phenotypic characteristics of the cell. The activation of transcription factors may involve multiple intracellular signal transduction pathways that are activated by cell-surface receptors. Transcription factor proteins may also be directly activated by ligands such as vitamin A and D and glucocorticoids. These proteins have the ability to convert transient environmental signals into long-term changes in gene transcription. Post-translational modifications of transcription factors by acetylation, phosphorylation, and nitration can impact their ability to bind to the DNA-or may affect their transcriptional activity.

Transcription factors are proteins that bind to the upstream regulatory elements of genes in the promoter and enhancer regions of DNA and stimulate or inhibit gene expression and protein synthesis. They play critical roles in embryogenesis and development. Transcription factors may be tissue specific or may be present in a variety of different tissue types. Many of the so-called tissue-specific transcription factors, however, are not restricted to a single tissue type. One such case is the thyroid transcription factor-1 (TTF-1) which is present both in thyroid follicular cells and in lung.

Transcription factors act within larger multiprotein complexes and often act positively to sustain their own expression. Transcription factors play critical roles in embryogenesis and development, hematopoiesis. Impaired activity of transcription factors has been linked to several malignancies.