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114:(in cell) studies have shown that eukaryotic polysomes exhibit linear configurations. Densely packed 3-D helices and planar double-row polysomes were found with variable packing including “top-to-top” contacts similar to prokaryotic polysomes. Eukaryotic 3-D polyribosomes are similar to prokaryotic 3-D polyribosomes in that they are “densely packed left-handed helices with four ribosomes per turn”. This dense packing can determine their function as regulators of translation, with 3-D polyribosomes being found in sarcoma cells using fluorescence microscopy.
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corresponding to mRNA are revealed by the measurement of total protein across the gradient. The corresponding mRNA is associated with increasing numbers of ribosomes as polysomes. The presence of mRNA across the gradient reveals the translation of the mRNA. Polysomal profiling is optimally applied to cultured cells and tissues to track the translational status of an identified mRNA as well as measure ribosome density. This technique has been used to compare the translational status of mRNAs in different cell types.
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determine structure. Different structural configurations of polyribosomes could reflect a variety in translation of mRNAs. An investigation of the ratio of polyribosomal shape elucidated that a high number of circular and zigzag polysomes were found after several rounds of translation. A longer period of translation caused the formation of densely packed 3-D helical polysomes. Different cells produce different structures of polysomes.
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Polyribosomes bound to membranes are restricted by a 2 dimensional space given by the membrane surface. The restriction of inter-ribosomal contacts causes a round-shape configuration that arranges ribosomes along the mRNA so that the entry and exit sites form a smooth pathway. Each ribosome is turned
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when ribosomes and elongation factors synthesize the encoded polypeptide. Multiple ribosomes move along the coding region of mRNA, creating a polysome. The ability of multiple ribosomes to function on an mRNA molecule explains the limited abundance of mRNA in the cell. Polyribosome structure differs
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Bacterial polysomes have been found to form double-row structures. In this conformation, the ribosomes are contacting each other through smaller subunits. These double row structures generally have a “sinusoidal” (zigzag) or 3-D helical path. In the “sinusoidal” path, there are two types of contact
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Electron microscopy technologies such as staining, metal shadowing, and ultra-thin cell sections were the original methods to determine polysome structure. The development of cryo-electron microscopy techniques has allowed for increased resolution of the image, leading to a more precise method to
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studies have shown that circular eukaryotic polysomes can be formed by free polyadenylated mRNA in the presence of initiation factor eIF4E bound to the 5’ cap and PABP bound to the 3’-poly(A) tail. However, this interaction between cap and the poly(A)-tail mediated by a protein complex is not a
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For example, polysomal profiling was used in a study to investigate the effect of vesicular stomatitis virus (VSV) in mammalian cells. The data from polysomal profiling showed that host mRNAs are outcompeted by viral mRNAs for polysomes, therefore decreasing the translation of host mRNA and
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is a technique that uses cycloheximide to arrest translation and a sucrose gradient to separate the resulting cell extract by centrifugation. Ribosome-associated mRNAs migrate faster than free mRNAs and polysome associated mRNAs migrate faster than ribosome associated mRNAs. Several peaks
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unique way of circularizing polysomal mRNA. It has been found that topologically circular polyribosomes can be successfully formed in the translational system with mRNA with no cap and no poly(A) tail as well as a capped mRNA without a 3’-poly(A) tail.
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between prokaryotic polysomes, eukaryotic polysomes, and membrane bound polysomes. Polysome activity can be used to measure the level of gene expression through a technique called polysomal profiling.
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between the small subunits- “top-to-top” or “top-to-bottom”. In the 3-D helical path, only “top-to-top” contact is observed.
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65:. Originally coined "ergosomes" in 1963, they were further characterized by Jonathan Warner, Paul M. Knopf, and
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Afonina ZA, Shirokov VA (January 2018). "Three-Dimensional
Organization of Polyribosomes- A Modern Approach".
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molecule like “beads” on a “thread”. It consists of a complex of an mRNA molecule and two or more
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This article is about the term in cell biology. For the term in crystallography, see
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Li S, Le B, Ma X, Li S, You C, Yu Y, et al. (December 2016). Qi J (ed.).
260:"Translatome profiling: methods for genome-scale analysis of mRNA translation"
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Polysomes are present in archaea, but not much is known about the structure.
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Several ribosomes synthesizing a polypeptide on the same mRNA strand
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French SL, Santangelo TJ, Beyer AL, Reeve JN (April 2007).
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relative to the previous one, resembling a planar spiral.
383:"Transcription and translation are coupled in Archaea"
480:Theoretical and experimental structure of polysome
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264:Briefings in Functional Genomics
122:Atomic force microscopy used in
72:Polysomes are formed during the
387:Molecular Biology and Evolution
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444:10.1371/journal.ppat.1007875
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21:Polysome (crystallography)
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196:10.1134/S0006297918140055
225:Cambra K (Spring 2017).
184:Biochemistry. Biokhimiia
354:"Staining (Microscopy)"
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400:10.1093/molbev/msm007
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495:Protein biosynthesis
227:"Paul M. Knopf, PhD"
190:(Suppl 1): S48–S55.
321:10.7554/eLife.22750
277:10.1093/bfgp/elu045
145:Polysomal profiling
61:instructions into
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90:Prokaryotic
314:: e22750.
156:References
102:Eukaryotic
140:Profiling
118:Cell free
81:Structure
67:Alex Rich
56:translate
52:ribosomes
489:Category
463:31226162
409:17237472
340:27938667
286:25380596
204:29544430
124:in vitro
107:In cells
44:ergosome
40:polysome
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240:24 July
212:3745602
112:in situ
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59:mRNA
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