Telomerase repressor proteins and nucleic acid compositions encoding the same are provided. The subject repressor proteins bind to a repressor site in the TERT minimal promoter, e.g., a Site C site, and thereby inhibit TERT expression. Also provided are methods of modulating, e.g., inhibiting or enhancing, TERT expression. The subject invention finds use in a variety of different applications, including therapeutic and therapeutic agent screening applications.