Biology subjects

Greider, C. W.

Publications and source records attributed to Greider, C. W..

3 recordsLinked to original sources

bioRxiv2018

TIN2 functions with TPP1/POT1 to stimulate telomerase processivity

Telomere length maintenance is crucial for cells that divide many times. TIN2 is an important regulator of telomere length, and mutations in TINF2, the gene encoding TIN2, cause short telomere syndromes. While the genetics underscore the importance of TIN2, the mechanism through which TIN2 regulates telomere length remains unclear. Here, we characterize the effects of TIN2 on telomerase activity. We identified a new isoform in human cells, TIN2M, that is expressed at similar levels to previously studied TIN2 isoforms. Additionally, we found that all three TIN2 isoforms stimulated telomerase processivity beyond the previously characterized stimulation by TPP1/POT1. Mutations in the TPP1 TEL-patch abrogated this stimulation, implicating TIN2 as a component of the TPP1/POT1 processivity complex. All three TIN2 isoforms localized to telomeres in vivo but had distinct effects on telomere length, suggesting they are functionally distinct. These data contrast previous descriptions of TIN2 a simple scaffolding protein, showing that TIN2 isoforms directly regulate telomerase.

molecular biology↗

bioRxiv2017

Diagnostic utility of telomere length measurement in a hospital setting

Very short telomere length (TL) provokes cellular senescence in vitro, but the clinical utility of TL measurement in a hospital-based setting has not been determined. We tested the diagnostic and prognostic value of TL measurement by flow cytometry and fluorescence in situ hybridization (flowFISH) in individuals with mutations in telomerase and telomere maintenance genes, and examined prospectively whether TL altered treatment decisions for patients with bone marrow failure. TL had a definable normal range across populations with discrete lower and upper boundaries. TL above the 50th age-adjusted percentile had a 100% negative predictive value for clinically relevant mutations in telomere maintenance genes, but the lower threshold for diagnosis was age-dependent. The extent of deviation from the age-adjusted median correlated with the age at diagnosis of a telomere syndrome as well as the predominant complication. Mild short telomere defects manifested in adults as pulmonary fibrosis-emphysema, while severely short TL manifested in children as bone marrow failure and immunodeficiency. Among 38 newly diagnosed patients with bone marrow failure, TL shorter than the 1st age-adjusted percentile enriched for patients with germline mutations in inherited bone marrow failure genes, such as RUNX1, in addition to telomere maintenance genes. The TL result modified the hematopoietic stem cell donor choice and/or treatment regimen in one-fourth of the cases (9 of 38,24%). TL testing by flowFISH has diagnostic and predictive value in definable clinical settings. In patients with bone marrow failure, it altered treatment decisions for a significant subset.

genetics↗

bioRxiv2017

BRD4 inhibitors block telomere elongation

Cancer cells maintain telomere length equilibrium to avoid senescence and apoptosis induced by short telomeres, which are triggered by the DNA damage response. Limiting the potential for telomere maintenance in cancer cells has been long been proposed as a therapeutic target. Using an unbiased shRNA screen targeting known kinases, we identified bromodomain 4 (BRD4) as a telomere length regulator. Four independent BRD4 inhibitors blocked telomere elongation, in a dose dependent manner, in mouse cells overexpressing telomerase. Long-term treatment with BRD4 inhibitors caused telomere shortening in both mouse and human cells, suggesting BRD4 plays a role in telomere maintenance in vivo. Telomerase enzymatic activity was not directly affected by BRD4 inhibition. BRD4 is in clinical trials for a number of cancers, but its effects on telomere maintenance have not been previously reported investigated.

molecular biology↗