Crystal structure of an essential telomerase‐specific domain of TERT

Abstract

Telomerase is the ribonucleoprotein enzyme responsible for the addition of short telomeric DNA repeats to the ends of linear chromosomes. Our goal is to understand the structural basis for telomerase activity and regulation. Towards that end, we have determined the high-resolution crystal structure of a portion of the telomerase reverse transcriptase (TERT), the Telomerase Essential N-terminal (TEN) domain from Tetrahymena thermophila. The structure represents a novel mixed alpha-beta fold with a C-terminal extension that becomes ordered only upon interaction with other macromolecules. The positively charged C-terminus is involved in binding RNA in a sequence-nonspecific manner, analogous in a general sense to the interactions of certain ribosomal proteins with ribosomal RNA. These C-terminal amino acids, as well as conserved amino acids in a deep groove on the surface of the domain, are critical for TERT catalytic activity. The ability of the TEN domain to bind both RNA and telomeric DNA, coupled with the unexpectedly strong effects on activity upon mutagenesis of single surface amino acids, suggest that this domain contributes directly to catalysis by the telomerase core enzyme. This work was supported by the Howard Hughes Medical Institute.