Provided herein is a synthetic or isolated polynucleotide encoding a mammalian 18S rRNA that is resistant to pactamycin. The pactamycin-resistance is conferred by one or more single residue substitutions in the 18S rRNA sequence; a fragment thereof harboring said substitutions; a complementary sequence thereto; or a substantially identical sequence of the foregoing. Related systems, methods and kits are also described.