Transcription factors

In the field of molecular biology, a transcription factor (sometimes called a sequence-specific DNA binding factor) is a protein that binds to specific parts of DNA using DNA binding domains and is part of the system that controls the transfer (or transcription) of genetic information from DNA to RNA.
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Proteins that are directly involved in regulation of transcription initiation by binding to the control elements and allowing RNA polymerase to act. There are ubiquitous transcription factors as well as cell and tissue-specific ones. Several families have been identified including helix-loop-helix proteins, helix-turn-helix proteins, leucine zipper proteins and zinc finger proteins.