Final answer:
The mediator is a co-activator protein that binds to activators and PIC proteins to enhance transcription.
It does not bind just to DNA polymerase or directly interact with repressors or insulators
Step-by-step explanation:
The mediator is a co-activator protein that binds to activators and PIC proteins to enhance transcription. An activator is a regulatory protein that promotes transcription by enhancing the interaction of RNA polymerase with the promoter, while PIC (Pre-Initiation Complex) proteins are a group of proteins that assemble at the promoter of a gene to prepare for transcription initiation. Therefore, option 3) binds to activators and PIC proteins that enhance transcription is the correct statement.
The mediator interacts with activator proteins and the preinitiation complex, including RNA polymerase II, to enhance transcription. It does not bind just to DNA polymerase or directly interact with repressors or insulators.
The mediator is a co-activator protein that primarily functions to bridge the interaction between activator proteins and the preinitiation complex (PIC), which includes RNA polymerase II and various transcription factors required for the initiation of transcription. Thus, the correct answer to the student's question is that the mediator binds to activators and PIC proteins to enhance transcription. This interaction facilitates the bending of DNA that promotes the efficient initiation of transcription by RNA polymerase II. The mediator does not bind just to DNA polymerase, as DNA polymerase is involved in DNA replication rather than transcription. In addition, it does not typically interact directly with repressors or insulators in this context.