Regulation in eukaryotic transcription:
Transcription factors can be broadly divided into two classes: recruitment and activation of the transcriptional apparatus, and chromatin remodeling or modifying enzymes. Importantly, many of the transcriptional complexes many subunits and appear to assemble in a modular fashion. The many different combinatorial interactions are possible in distinct patterns of gene expression.
Thus, transcription of a gene is the major way of regulation of gene expression in eukaryotes. The complexity of the eukaryotic gene expression needs its own promoter. Eukaryotic genes are regulated by transcription activators called as transcription factors.