Answer:
Repressor protein
Step-by-step explanation:
Repressor is a protein that binds to deoxyribonucleic acid(DNA) or ribonucleic acid(RNA) it inhibits the expression of one or more genes which is done by binding to the associated silencers.
A DNA binding repressor works by blocking the attachment of RNA polymerase an enzyme that enhance transcription to the promoter, thus preventing genes from been transcribed into messenger RNA.
An RNA binding repressor binds to the messenger RNA and prevents translation of the bases on the messenger RNA into protein. The blocking of expression is called repression.