What are the Key Catalytic Steps in Transcription Initiation?
1. Promoter Recognition and Binding: The initial catalytic step involves the recognition and binding of the promoter region by the TATA-binding protein and TFIID complex. This step is crucial for positioning RNA polymerase II correctly at the start site of transcription.
2. Formation of the Pre-Initiation Complex: The subsequent assembly of general transcription factors and RNA polymerase II forms the pre-initiation complex (PIC). Each factor's binding is a catalytic event that stabilizes the complex and prepares it for transcription initiation.
3. Phosphorylation of RNA Polymerase II: The kinase activity of TFIIH catalyzes the phosphorylation of the C-terminal domain (CTD) of RNA polymerase II. This phosphorylation is essential for the transition from initiation to elongation of the RNA transcript.
