SAT-LB138 The LncRNA Growth Arrest Specific 5 Regulates Cell Survival via Distinct Structural Modules With Independent Functions

Frank, Filipp; Kavousi, Nadieh; Bountali, Aikaterina; Dammer, Eric; Mourtada-Maarabouni, Mirna; Ortlund, Eric

Abstract

The growth arrest-specific 5 (gas5) gene encodes a long non-coding RNA (lncRNA) that is required for normal growth arrest, slows down the cell cycle, controls apoptosis, and is required for the inhibition of cell growth by mTOR inhibitors such as rapamycin. In agreement with this role in regulating cell proliferation, Gas5 expression is reduced and acts as a tumor suppressor in numerous cancers, including B-cell lymphoma and leukemia. At its 3’ terminal end (nucleotides 546-566) Gas5 contains a predicted stem-loop structure that specifically interacts with steroid receptors (SRs) and blocks DNA-dependent steroid signalling. In steroid-sensitive cancer cells such as prostate cancers this SR binding motif is responsible for Gas5 effects on cell growth. This is not true in other cell types, however, where proliferation is not strongly dependent on SR signaling (e.g. leukemic T cells). Therefore, other regions in Gas5 must be active and use different mechanisms to regulate cell survival. We have used SHAPE chemical probing to analyze the secondary structure of Gas5 in vitro and in cellulo. We find that the secondary structure of endogenous Gas5 resembles that of in vitro transcribed Gas5 RNA. The molecule contains three separate structural modules: a 5’ module with low secondary structure content, a highly structured core module, and the SR binding module, which forms separate from the rest of the molecule close to its 3’ end. Functional studies in leukemic T cells show that the 5’ module mediates Gas5’s role in inhibiting basal cell survival and slowing the cell cycle, whereas the core module is required for mediating the effects of mTOR inhibition. These results confirm that the Gas5 structural modules function independently in cells and each module acts under different cellular conditions, likely using different molecular mechanisms. RNA pull-downs from cell lysates using the identified modules and full-length RNA identified proteins preferentially associated with each module. Proteins preferentially associated with the 5’ terminal region are enriched in splicing and RNA processing factors. The structured central region preferentially interacts with proteins involved in chromosome organization such as the SWI/SNF family of nucleosome remodeling complexes.

Citation

Frank, F., Kavousi, N., Bountali, A., Dammer, E., Mourtada-Maarabouni, M., & Ortlund, E. (2020). SAT-LB138 The LncRNA Growth Arrest Specific 5 Regulates Cell Survival via Distinct Structural Modules With Independent Functions. Journal of the Endocrine Society, https://doi.org/10.1210/jendso/bvaa046.2327

• Journal Article Type: Conference Paper
• Acceptance Date: Feb 28, 2020
• Publication Date: May 8, 2020
• Journal: Journal of the Endocrine Society
• Print ISSN: 2472-1972
• Publisher: Oxford University Press
• Series Title: The Annual Meeting of the Endocrine Society – March 28 – 31, 2020 - San Francisco, California
• DOI: https://doi.org/10.1210/jendso/bvaa046.2327
• Publisher URL: https://academic.oup.com/jes/article/4/Supplement_1/SAT-LB138/5833706