High impact information on EST3

• Yeast telomerase is thought to be a holoenzyme containing Est2p and TLC1 RNA, the catalytic subunit and its intrinsic template, respectively, as well as the TLC1-RNA-associated factors Est1p and Est3p [1].
• N-terminal domain of yeast telomerase reverse transcriptase: recruitment of Est3p to the telomerase complex [2].
• Overexpression of telomerase component Est3p led to allele-specific suppression of the temperature-sensitive mutations in region I, suggesting that Est3p interacts with this protein domain [2].
• In contrast, mutations in EST1, EST3 or CDC13 eliminate telomere replication in vivo [1] [6] [7] [8] but are dispensable for in vitro telomerase catalytic activity [2] [9] [3].
• We show here that Est3p is a stable component of the telomerase holoenzyme and furthermore, association of Est3p with the enzyme requires an intact catalytic core [3].

Biological context of EST3

• These data suggested that dimerization is important for Est3p function in vivo [4].
• Double point mutation of Est3p-D49A-K68A and single point mutation of Est3p-K68A showed similar telomere shortening, suggesting that the K68 residue might be more important for telomerase activity [4].
• The ectopic co-expression of K71A or T115A mutant with wild-type Est3p using centromere plasmids caused telomere shortening, while co-expression of the D49A, K68A, D86A or F103A mutants with wild-type Est3p had no effect on telomere length regulation [4].
• RESULTS: We identified a potential site of +1 ribosomal frameshifting in the EST3 coding sequence and demonstrated that translation both upstream and downstream of this site is required for EST3 function [5].
• Immunoblot analysis revealed that two proteins were synthesized from EST3: a truncated protein resulting from translation of only the first open reading frame, as well as the full-length 181 amino-acid Est3 protein resulting from translation through the frameshift site [5].

Anatomical context of EST3

• These data suggest that the EST3 stimulator may modulate access by aminoacyl-tRNAs to the ribosomal A site by interacting with several targets in a ribosome paused during elongation [6].

Physical interactions of EST3

• The absence of Est1p and Est3p from the complex during G1 phase can be attributed to proteasome-dependent degradation of Est1p [7].

Other interactions of EST3

• EST1, EST2, EST3 and TLC1 function in a single pathway for telomere replication in the yeast Saccharomyces cerevisiae [1] [2], as would be expected if these genes all encode components of the same complex [3].
• We find that frameshifting has persisted in two structural genes in budding yeasts, ABP140 and EST3 for about 150 million years [8].

References