Conserved Pseudoknots in lncRNA MEG3 Are Essential for Stimulation of the p53 Pathway.

Tina Uroda,Marco Marcia,Paolo Annibale,Annalisa Rossi,Ombeline Pessey,Jean-Marie Teulon,Jean-Luc Pellequer,Alberto Inga,Isabel Chillón,Eleni Anastasakou

doi:10.1016/j.molcel.2019.07.025

Abstract

SummaryLong non-coding RNAs (lncRNAs) are key regulatory molecules, but unlike with other RNAs, the direct link between their tertiary structure motifs and their function has proven elusive. Here we report structural and functional studies of human maternally expressed gene 3 (MEG3), a tumor suppressor lncRNA that modulates the p53 response. We found that, in an evolutionary conserved region of MEG3, two distal motifs interact by base complementarity to form alternative, mutually exclusive pseudoknot structures (“kissing loops”). Mutations that disrupt these interactions impair MEG3-dependent p53 stimulation in vivo and disrupt MEG3 folding in vitro. These findings provide mechanistic insights into regulation of the p53 pathway by MEG3 and reveal how conserved motifs of tertiary structure can regulate lncRNA biological function.

Highlights

Long non-coding RNA structures are increasingly being recognized as important modulators of cellular processes, including chromatin remodeling, DNA repair, and translation (Mercer et al, 2009)
In an evolutionary conserved region of maternally expressed gene 3 (MEG3), two distal motifs interact by base complementarity to form alternative, mutually exclusive pseudoknot structures (‘‘kissing loops’’)
Mutations that disrupt these interactions impair MEG3-dependent p53 stimulation in vivo and disrupt MEG3 folding in vitro. These findings provide mechanistic insights into regulation of the p53 pathway by MEG3 and reveal how conserved motifs of tertiary structure can regulate Long non-coding RNAs (lncRNAs) biological function

Summary

Introduction

Long non-coding RNA (lncRNA) structures are increasingly being recognized as important modulators of cellular processes, including chromatin remodeling, DNA repair, and translation (Mercer et al, 2009). Human maternally expressed gene 3 (MEG3) is an alternatively spliced nuclear lncRNA abundant in the brain, placenta, and endocrine glands (Mondal et al, 2015; Zhang et al, 2003). In embryonic cells, where it is not imprinted (McMurray and Schmidt, 2012), MEG3 silences genes involved in neurogenesis by regulating chromatin targeting of Polycomb proteins, and MEG3 expression is needed during neuronal development (Kaneko et al, 2014; Mercer et al, 2008; Mondal et al, 2015). Understanding the molecular mechanism of MEG3 is crucial to improve our knowledge of specific p53-related carcinogenic pathways

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Conclusion