RG/RGG motif explained

The arginine-glycine or arginine-glycine-glycine (RG/RGG) motif is a repeating amino acid sequence motif commonly found in RNA-binding proteins (RBPs). RGG regions in proteins are defined as two or more RG/RGG sequences within a stretch of 30 amino acids.^[1] Initially named the RGG box, it confers a protein with the ability to bind double-stranded mRNA molecules.^[2] The RGG motif has been observed in proteins from at least 12 animal species, including humans.^[3]

Biochemical function

RGG motifs are primarily involved in mediating protein-RNA interactions. Positive charges from arginine residues promote electrostatic interactions with mRNA molecules. The composition and structure of the arginine side chain may also allow for specific interactions with other molecules as opposed to the other positively charged amino acids, lysine and histidine.^[4] Glycine residues add flexibility to the peptide structure and promote their tendency to form intrinsically disordered regions. The RGG motif can also drive liquid-lipid phase separation of proteins inside cells as well as in vitro.^{[5] [6]}

Synthetic uses

Researchers have pursued creating condensates with novel functions for use in cellular and metabolic engineering. Synthetically designed proteins containing repeating RGG motifs have been used to form droplets with tunable properties in cells and in vitro.^{[7] [8]}

Notable RGG-containing proteins

RGG motif-containing proteins are the second most abundant group of RBPs in the human genome.^{[9] [10]} They are involved in various RNA metabolism, export, and translation functions.

• Sbp1^[11]
• Npl3^{[12] [13]}
• Ded1^[14]
• FMR1^[15]
• FUS^{[16] [17]}
• Laf-1^[18]

Notes and References

1. Chowdhury . The RGG motif proteins: Interactions, functions, and regulations . WIREs RNA . 2023 . 14. 1 . e1748 . 10.1002/wrna.1748 . 35661420 . 9718894 .
2. Kiledjian . Primary structure and binding activity of the hnRNP U protein: binding RNA through RGG box . EMBO J . 1992 . 11 . 7 . 2655–2664. 10.1002/j.1460-2075.1992.tb05331.x . 1628625 . 556741 .
3. Qian . Synthetic protein condensates for cellular and metabolic engineering . Nat. Chem. Biol. . 2022 . 18 . 12 . 1330–1340. 10.1038/s41589-022-01203-3 . 36400990 .
4. Takahama . Identification of Ewing's sarcoma protein as a G-quadruplex DNA- and RNA-binding protein . FEBS J. . 2011 . 278 . 6 . 988–998. 10.1111/j.1742-4658.2011.08020.x . 21244633 .
5. Qian . Synthetic protein condensates for cellular and metabolic engineering . Nat. Chem. Biol. . 2022 . 18 . 12 . 1330–1340. 10.1038/s41589-022-01203-3 . 36400990 .
6. Robinson . Cell-Free Expressed Membraneless Organelles Sequester RNA in Synthetic Cells . bioRxiv . 2023 . 10.1101/2023.04.03.535479 . 37066403 . 10104018 .
7. Schuster . Controllable protein phase separation and modular recruitment to form responsive membraneless organelles . Nat Commun . 2018 . 9 . 1 . 2985. 10.1038/s41467-018-05403-1 . 30061688 . 6065366 . 2018NatCo...9.2985S .
8. Dai . Engineering synthetic biomolecular condensates. . Nat Rev Bioeng . 2023 . 1 . 7 . 466–480. 10.1038/s44222-023-00052-6 . 37359769 . 10107566 .
9. Ozdilek . Intrinsically disordered RGG/RG domains mediate degenerate specificity in RNA binding . Nucleic Acids Res. . 2017 . 45 . 13 . 7984–7996. 10.1093/nar/gkx460 . 28575444 . 5570134 .
10. Hentze . A brave new world of RNA-binding proteins . Nat. Rev. Mol. Cell Biol. . 2018 . 19 . 5 . 327–341. 10.1038/nrm.2017.130 . 29339797 .
11. Jong . Saccharomyces cerevisiae SSB1 protein and its relationship to nucleolar RNA-binding protein . Mol. Cell. Biol. . 1987 . 19 . 2947–2955.
12. Bossie . A mutant nuclear protein with similarity to RNA binding proteins interferes with nuclear import in yeast . Mol. Biol. Cell . 1992 . 3 . 8 . 875–893. 10.1091/mbc.3.8.875 . 1392078 . 275646 .
13. Flach . A yeast RNA-binding protein shuttles between the nucleus and the cytoplasm . Mol. Cell. Biol. . 1994 . 14 . 12 . 8399–8407. 10.1128/mcb.14.12.8399-8407.1994 . 7969175 . 359379 .
14. Iost . Ded1p, a DEAD-box protein required for translation initiation in Saccharomyces cerevisiae, is an RNA helicase . J. Biol. Chem. . 1999 . 274 . 25 . 17677–17683. 10.1074/jbc.274.25.17677 . free . 10364207 .
15. Ashley . FMR1 protein: conserved RNP family domains and selective RNA binding. . Science . 1993 . 263 . 5133 . 563–566. 10.1126/science.7692601 . 7692601 . 1993Sci...262..563A .
16. Crozat . Fusion of CHOP to a novel RNA-binding protein in human myxoid liposarcoma. Nature . 1993 . 363 . 6430 . 640–644. 10.1038/363640a0 . 8510758 . 1993Natur.363..640C .
17. Baechtold . Human 75-kDa DNA-pairing protein is identical to the pro-oncoprotein TLS/FUS and is able to promote D-loop formation . J. Biol. Chem. . 1999 . 274 . 48 . 34337–34342. 10.1074/jbc.274.48.34337 . free . 10567410 .
18. Elbaum-Garfinkle . The disordered P granule protein LAF-1 drives phase separation into droplets with tunable viscosity and dynamics. . Proc. Natl. Acad. Sci. . 2015 . 112 . 23 . 7189–7194. 10.1073/pnas.1504822112 . free . 26015579 . 4466716 . 2015PNAS..112.7189E .