Final answer:
Accessory proteins that accelerate nucleation include activator proteins, which enhance interactions with RNA polymerase, and proteins associated with nuclear bodies, aiding in the assembly of the transcription initiation complex.
Step-by-step explanation:
The two accessory proteins that accelerate nucleation and are essential in the process of transcription initiation in eukaryotic cells are activator proteins and specific nuclear bodies associated with proteins.
Activator proteins enhance the interaction between RNA polymerase and a particular promoter, facilitating the attraction and stabilization of the transcription initiation complex. This effect is often accomplished through an induced conformational change in DNA, thanks to the binding of these proteins to enhancers. On the other hand, nuclear bodies are structures within the nucleus that, along with their associated proteins, help in the assembly and function of the spliceosomal small nuclear ribonucleoproteins (snRNPs), which are critical for the splicing of pre-mRNA and necessary for proper gene expression.