What are basal transcription factors?

Basal transcription factors are specific proteins that bind with DNA to begin transcription, the process of DNA being copied into primary transcript mRNA. Basal transcription factors are also important in regulating gene expression.

In bacteria, a single basal transcription factor is required along with an RNA polymerase to begin the process of gene expression. In eukaryote cells, such as those in plants and animals, transcription requires RNA polymerase II and multiple basal transcription factors. The portion of DNA transcribed into primary transcript mRNA is called a transcriptor unit. The larger the genome size of an organism, the larger the number of basal transcription factors that it possesses.