Final answer:
In eukaryotic cells, repressor proteins can decrease transcription by preventing the assembly of the transcription initiation complex, aligning with option C from the choices provided.
Step-by-step explanation:
Eukaryotic repressor proteins can decrease transcription using various mechanisms. One of these mechanisms involves the repressor protein binding to the promoter or enhancer regions to physically block transcription, which prevents the assembly of the transcription initiation complex, aligning with option C. Repressors respond to external stimuli to prevent the binding of activating transcription factors necessary for initiating transcription.
Another mechanism involves changing the structure of chromatin, such as through DNA methylation or histone modification, which can either increase or decrease transcription; however, the recruitment of a histone acetyltransferase complex, mentioned in option B, would typically modify histones in a way that enhances transcription, not decreases it.
Because eukaryotic cells lack an operon structure, the mechanism described in option A is specific to prokaryotic regulatory systems. Attracting a chromatin remodeling complex as mentioned in option D is generally associated with opening chromatin to facilitate transcription, contrary to the function of a repressor.