Final answer:
The 'commitment factor' for specifying the start point for RNA polymerase I transcription is the SL1 complex.
Step-by-step explanation:
The complex that acts as the "commitment factor" to specify the start point for RNA polymerase I transcription is SL1.
In eukaryotic transcription, various transcription factors and complexes are involved in the initiation of transcription by RNA polymerase I, II, and III.
Specifically, RNA polymerase I transcription is initiated when the SL1 complex, along with the Upstream Binding Factor (UBF), binds to the core promoter region to form the pre-initiation complex. This marks the commitment of the complex to initiate transcription.
The initiation complex, in general, is a combination of transcription factors and RNA polymerase bound to a promoter.