Final answer:
RPA is a protein essential for DNA replication, functioning at the replication fork to stabilize single-stranded DNA.
Step-by-step explanation:
Replication Protein A (RPA) is a protein responsible for stabilizing single-stranded DNA during replication and repair processes. It is not an enzyme involved in RNA processing, a ribosomal protein aiding in protein synthesis, nor a transcription factor regulating gene expression.
Instead, it plays a crucial role in DNA replication, particularly at the replication fork where it binds to single-stranded DNA to prevent it from winding back into a double helix, allowing replication to proceed efficiently.