Explain the role of transcription factors in eukaryotic gene expression.

Eukaryotic transcription factors (TFs) are proteins that regulate gene expression by binding to specific DNA sequences. General TFs (TFIIA, TFIIB, TFIID, TFIIE, TFIIF, TFIIH) are required for basal transcription from all promoters and assemble with RNA Pol II at the promoter. Specific TFs (activators and repressors) bind enhancers, silencers, or response elements to modulate transcription rates. They work through recruitment of coactivators, chromatin remodelers, or the mediator complex. Combinatorial control by multiple TFs allows precise spatial and temporal gene regulation.