Roles of telomerase reverse transcriptase N-terminal domain in assembly and activity of Tetrahymena telomerase holoenzyme.
ABSTRACT Telomerase extends chromosome ends by the addition of single-stranded telomeric repeats. To support processive repeat synthesis, it has been proposed that coordination occurs between DNA interactions with the telomerase RNA template, the active site in the telomerase reverse transcriptase (TERT) core, a TERT N-terminal (TEN) domain, and additional subunits of the telomerase holoenzyme required for telomere elongation in vivo. The roles of TEN domain surface residues in primer binding and product elongation have been studied largely using assays of minimal recombinant telomerase enzymes, which lack holoenzyme subunits that properly fold and conformationally stabilize the ribonucleoprotein and/or control its association with telomere substrates in vivo. Here, we use Tetrahymena telomerase holoenzyme reconstitution in vitro to assess TEN domain sequence requirements in the physiological enzyme context. We find that TEN domain sequence substitutions in the Tetrahymena telomerase holoenzyme influence synthesis initiation and elongation rate but not processivity. Functional and direct physical interaction assays pinpoint a conserved TEN domain surface required for holoenzyme subunit association and for high repeat addition processivity. Our results add to the understanding of telomerase holoenzyme architecture and TERT domain functions with direct implications for the unique mechanism of single-stranded repeat synthesis.
Article: Balancing instability: dual roles for telomerase and telomere dysfunction in tumorigenesis.[show abstract] [hide abstract]
ABSTRACT: Telomere shortening and telomerase activation both occur in human tumors. Telomere shortening has been proposed to have two conflicting roles in tumorigenesis: tumor suppression and initiation of chromosomal instability. Similarly, while telomerase activation is suggested to be necessary for tumor growth, telomerase may help to stabilize genomic instability. Here we review what is known about these conflicting roles and propose a framework to understand the role of telomerase in cancer progression.Oncogene 02/2002; 21(4):619-26. · 6.37 Impact Factor