Stress Granules and P-Bodies: An Insight into mRNA Translational Control and Decay
Posttranscriptional control of gene expression in the cytoplasm is an important regulatory step for protein level maintenance and thereby for cellular homeostasis. It plays an important role in various cellular processes such as development & differentiation, learning & memory and, aging & regeneration.
RNA granules are RNA-protein complexes formed due to protein-protein and protein-RNA interaction. Various cellular cues such as nutritional and oxidative stress, heat shock, unfolded or dysregulated proteins in the cell trigger assembly of RNA granules. RNA granules (also termed as higher order messenger ribo-nucleoprotein complexes - mRNPs) have been proposed to play a role in posttranscriptional gene regulation specifically mRNA transport, translation, and decay.
Few cellular proteins and pathways have been reported to play important role in modulating RNA granules. Proteins with low complexity (LC) regions or intrinsically disordered regions (IDR) play an important role in granule assembly. Stress granules (SGs) and mRNA processing bodies (PBs) are two of the well-characterized conserved granule types. Both SGs and PBs contain translationally repressed mRNAs however processing bodies (PBs) also contain mRNAs undergoing degradation. Consistent with that, P-bodies contain protein factors involved in mRNA decapping and degradation whereas these factors are largely excluded from stress granules. Other granule types are Transport granules, Neuronal granules, and Germ granules. Mutations in RNA granule components leading to impaired assembly and disassembly of granules have been implicated in Neurodegenerative diseases and Cancers.
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