Ratcheted transport and sequential assembly of the yeast telomerase RNP

• Published in: Cell reports (Cambridge) Vol. 42; no. 12; p. 113565
• Main Authors: Neumann, Hannah, Bartle, Louise, Bonnell, Erin, Wellinger, Raymund J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 26.12.2023; Elsevier
• Subjects: CP: Molecular biology; RNA - metabolism; RNP assembly; RNP transport; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - metabolism; telomerase; Telomerase - metabolism; Telomere - metabolism; telomere replication; CP: Molecular biology; telomere replication; telomerase; RNP transport; RNP assembly
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2023.113565

The telomerase ribonucleoprotein particle (RNP) replenishes telomeric DNA and minimally requires an RNA component and a catalytic protein subunit. However, telomerase RNP maturation is an intricate process occurring in several subcellular compartments and is incompletely understood. Here, we report how the co-transcriptional association of key telomerase components and nuclear export factors leads to an export-competent, but inactive, RNP. Export is dependent on the 5′ cap, the 3′ extension of unprocessed telomerase RNA, and protein associations. When the RNP reaches the cytoplasm, an extensive protein swap occurs, the RNA is trimmed to its mature length, and the essential catalytic Est2 protein joins the RNP. This mature and active complex is then reimported into the nucleus as its final destination and last processing steps. The irreversible processing events on the RNA thus support a ratchet-type model of telomerase maturation, with only a single nucleo-cytoplasmic cycle that is essential for the assembly of mature telomerase. [Display omitted] •Telomerase is generated via distinct intermediate RNPs of changing composition•The co-transcriptionally formed RNP is inactive and contains the CBC, Yku, and Sm proteins•Telomerase RNA is matured in the cytoplasm, where Est2 association completes RNP assembly•The re-imported mature telomerase remains in the nucleus for the rest of its life cycle Neumann et al. show that the generation of the mature yeast telomerase RNP is a very dynamic process. The ratcheted mechanism is based on irreversible RNA processing events occurring in distinct subcellular compartments. An early catalytically inactive RNP passes only once through the cytoplasm for RNP completion and quality control.