All the cellular processes in living cells such as growth, development, morphogenesis and cellular differentiation are a product of gene expression programs involving complicated transcriptional regulation of several genes. This process of transcriptional regulation is tightly controlled and coordinated by proteins called transcriptional regulators. These transcriptional regulators and factors are DNA-binding proteins that bind to the promoter or enhancer sequences on the DNA and facilitate either transcriptional repression or activation.
There are three principal types of transcription factors. These include basal transcription factors, upstream transcription factors and inducible transcription factors. The basic structure of every transcriptional factor mainly contains a DNA-binding domain and an activator domain. DNA-binding motifs found in transcription factors include zinc-finger, helix-loop-helix, helix-turn-helix, leucine zipper and high-mobility groups, based on which transcription factors are classified. The activator domain of these transcription factors interacts with components of transcription machinery such as RNA polymerases and associated transcription regulators.
Regulation of transcriptional factors is a complex mechanism that ensures exact spatio-temporal expression of genes. In response to a specific cellular stimulus, these trans-regulatory factors are activated in a sequential manner. Upon activation, these factors recruit transcriptional co-regulators such as histones that function as co-activators or co- repressors and aid in modifying chromatin structure. Altered activation of these regulators is often associated with various pathologies such as chronic disorders and malignancies. Recent studies are concentrating on developing improved disease treatment strategies through identification of different transcription factor-binding patterns and blocking them.
There are several families of trans-regulatory factors that control critical cellular signaling cascades involved in cell proliferation, survival, lineage development and cellular differentiation. These include Rel/NF-kB family, AP-1 family, STAT family of transcription factors, homeodomain proteins, DNA-binding proteins, POU transcription factors, nuclear hormone receptor family, p53 family and E2F family.