Eukaryotic transcription factors.

Many nuclear proteins have been found recently to interact with short conserved sequences which are involved in regulating the transcription of various genes. Nuclear transcription factors may be arbitrarily subdivided into two groups, ubiquitous and tissue-specific. The transcription of one gene is usually regulated by several factors which interact with different sequences located either in the promoter region of the gene or outside it. The appearance or disappearance of transcription factors for some genes corresponds to certain phases of cell differentiation or dedifferentiation and even to individual stages of the cell cycle.