Final answer:
Repressor proteins facilitate negative regulation of DNA replication by binding to the operator, which prevents RNA polymerase from initiating transcription.
Step-by-step explanation:
The molecule that enables or facilitates negative regulation of DNA replication is the repressor protein. This molecule binds to the DNA at a site known as the operator, which is located near the promoter region where RNA polymerase would bind to initiate transcription.
When the repressor is bound to the operator, it prevents the attachment of RNA polymerase to the promoter, thus inhibiting the initiation of transcription and subsequent DNA replication.