The role of filamentous membraneless organelle in 3UTR-mediated Protein-Protein interfaces and localization: TIGER Domain

• Published in: Supramolecular Materials 2024-12, Vol.3, p.100060, Article 100060
• Main Authors: Rahim, Kashif, Umair, Muhammad, Haq, Ihtisham Ul
• Format: Article
• Language: English
• Subjects: 3(UTR functions; Biomolecular condensates; ER-associated organelles; Membraneless organelles; Tiger domain; TIS granule; Tis11b; Translation
• ISSN: 2667-2405; 2667-2405
• DOI: 10.1016/j.supmat.2023.100060

Cells contain numerous membrane-less (MLOs) and multiple membrane-bound organelles. Most of the MLOs have a spherical shape except for a few organelles (that have a filamentous appearance, e.g. FXR1 condensates, L-bodies, and TIS granules). Some MLOs form associations with the membrane-bound organelles, such as the endoplasmic reticulum (ER). This fact was recently revealed by the discovery of a new, unique filamentous membrane-less organelle called "TIS granule" that was directly interlinked and twisted with the endoplasmic reticulum (ER). The most interesting insight of the TIS granules is that the transcribed genetic information carried by 3′ UTR of mRNA is translated by them, which makes them one of the most crucial sub-cellular organelles. Multiple TIS granules form a reticular meshwork with the endoplasmic reticulum (ER), ultimately creating an inter-organelle space or subcellular compartment known as the "TIGER Domain" that is enriched with membrane proteins-encoding mRNAs, some intermediate proteins (e.g. HuR) and a few chaperones. TIGER domain enables 3′ UTR-mediated protein–protein interactions (PPIs) between specific & functionally relevant proteins, such as membrane and 3′ UTR dependent proteins. For more than six decades, only ribosomes were credited as solo membrane-less organelles involved in the cell's translation process. However, this review acknowledges and highlights another less familiar translation companion of the ribosome (i.e. TIS granule) and elaborates on its composition, assembly, morphology and complete functionality in an easily understandable way.