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Chakraborty A, Dutta A, Dettori LG, Daoud R, Li J, Gonzalez L, Xue X, Hehnly H, Sung P, Bah A, Feng W. Complex interplay between FMRP and DHX9 during DNA replication stress. J Biol Chem 2024; 300:105572. [PMID: 38110032 PMCID: PMC10825048 DOI: 10.1016/j.jbc.2023.105572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 11/28/2023] [Accepted: 12/06/2023] [Indexed: 12/20/2023] Open
Abstract
Mutations in, or deficiency of, fragile X messenger ribonucleoprotein (FMRP) is responsible for the Fragile X syndrome (FXS), the most common cause for inherited intellectual disability. FMRP is a nucleocytoplasmic protein, primarily characterized as a translation repressor with poorly understood nuclear function(s). We recently reported that FXS patient cells lacking FMRP sustain higher level of DNA double-strand breaks (DSBs) than normal cells, specifically at sequences prone to forming R-loops, a phenotype further exacerbated by DNA replication stress. Moreover, expression of FMRP, and not an FMRPI304N mutant known to cause FXS, reduced R-loop-associated DSBs. We subsequently reported that recombinant FMRP directly binds R-loops, primarily through the carboxyl terminal intrinsically disordered region. Here, we show that FMRP directly interacts with an RNA helicase, DHX9. This interaction, which is mediated by the amino terminal structured domain of FMRP, is reduced with FMRPI304N. We also show that FMRP inhibits DHX9 helicase activity on RNA:DNA hybrids and the inhibition is also dependent on the amino terminus. Furthermore, the FMRPI304N mutation causes both FMRP and DHX9 to persist on the chromatin in replication stress. These results suggest an antagonistic relationship between FMRP and DHX9 at the chromatin, where their proper interaction leads to dissociation of both proteins from the fully resolved R-loop. We propose that the absence or the loss of function of FMRP leads to persistent presence of DHX9 or both proteins, respectively, on the unresolved R-loop, ultimately leading to DSBs. Our study sheds new light on our understanding of the genome functions of FMRP.
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Affiliation(s)
- Arijita Chakraborty
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Arijit Dutta
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center San Antonio, San Antonio, Texas, USA
| | - Leonardo G Dettori
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Rosemarie Daoud
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Jing Li
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Leticia Gonzalez
- Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas, USA
| | - Xiaoyu Xue
- Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas, USA
| | - Heidi Hehnly
- Department of Biology, Syracuse University, Syracuse, New York, USA
| | - Patrick Sung
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center San Antonio, San Antonio, Texas, USA
| | - Alaji Bah
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Wenyi Feng
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA.
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Dettori LG, Torrejon D, Chakraborty A, Dutta A, Mohamed M, Papp C, Kuznetsov VA, Sung P, Feng W, Bah A. A Tale of Loops and Tails: The Role of Intrinsically Disordered Protein Regions in R-Loop Recognition and Phase Separation. Front Mol Biosci 2021; 8:691694. [PMID: 34179096 PMCID: PMC8222781 DOI: 10.3389/fmolb.2021.691694] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 05/14/2021] [Indexed: 11/13/2022] Open
Abstract
R-loops are non-canonical, three-stranded nucleic acid structures composed of a DNA:RNA hybrid, a displaced single-stranded (ss)DNA, and a trailing ssRNA overhang. R-loops perform critical biological functions under both normal and disease conditions. To elucidate their cellular functions, we need to understand the mechanisms underlying R-loop formation, recognition, signaling, and resolution. Previous high-throughput screens identified multiple proteins that bind R-loops, with many of these proteins containing folded nucleic acid processing and binding domains that prevent (e.g., topoisomerases), resolve (e.g., helicases, nucleases), or recognize (e.g., KH, RRMs) R-loops. However, a significant number of these R-loop interacting Enzyme and Reader proteins also contain long stretches of intrinsically disordered regions (IDRs). The precise molecular and structural mechanisms by which the folded domains and IDRs synergize to recognize and process R-loops or modulate R-loop-mediated signaling have not been fully explored. While studying one such modular R-loop Reader, the Fragile X Protein (FMRP), we unexpectedly discovered that the C-terminal IDR (C-IDR) of FMRP is the predominant R-loop binding site, with the three N-terminal KH domains recognizing the trailing ssRNA overhang. Interestingly, the C-IDR of FMRP has recently been shown to undergo spontaneous Liquid-Liquid Phase Separation (LLPS) assembly by itself or in complex with another non-canonical nucleic acid structure, RNA G-quadruplex. Furthermore, we have recently shown that FMRP can suppress persistent R-loops that form during transcription, a process that is also enhanced by LLPS via the assembly of membraneless transcription factories. These exciting findings prompted us to explore the role of IDRs in R-loop processing and signaling proteins through a comprehensive bioinformatics and computational biology study. Here, we evaluated IDR prevalence, sequence composition and LLPS propensity for the known R-loop interactome. We observed that, like FMRP, the majority of the R-loop interactome, especially Readers, contains long IDRs that are highly enriched in low complexity sequences with biased amino acid composition, suggesting that these IDRs could directly interact with R-loops, rather than being “mere flexible linkers” connecting the “functional folded enzyme or binding domains”. Furthermore, our analysis shows that several proteins in the R-loop interactome are either predicted to or have been experimentally demonstrated to undergo LLPS or are known to be associated with phase separated membraneless organelles. Thus, our overall results present a thought-provoking hypothesis that IDRs in the R-loop interactome can provide a functional link between R-loop recognition via direct binding and downstream signaling through the assembly of LLPS-mediated membrane-less R-loop foci. The absence or dysregulation of the function of IDR-enriched R-loop interactors can potentially lead to severe genomic defects, such as the widespread R-loop-mediated DNA double strand breaks that we recently observed in Fragile X patient-derived cells.
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Affiliation(s)
- Leonardo G Dettori
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Diego Torrejon
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Arijita Chakraborty
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Arijit Dutta
- Department of Biochemistry and Structural Biology, University of Texas Health San Antonio, San Antonio, TX, United States
| | - Mohamed Mohamed
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Csaba Papp
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States.,Department of Urology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Vladimir A Kuznetsov
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY, United States.,Bioinformatics Institute, ASTAR Biomedical Institutes, Singapore, Singapore
| | - Patrick Sung
- Department of Biochemistry and Structural Biology, University of Texas Health San Antonio, San Antonio, TX, United States
| | - Wenyi Feng
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Alaji Bah
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
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