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The Scientific Basis of Medicine
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Chris O'Callaghan, Rachel Allen
When a gene is active, the chromatin structure loosens to allow access for RNA polymerase to generate an RNA molecule (Figure 2.8). This messenger RNA (mRNA) precursor is then processed for translation into an amino acid sequence. Gene splicing removes introns from the coding sequences to leave a continuous series of exons for translation. Once within the cytosol, mRNA attaches to large ribonucleoprotein particles known as ribosomes. Ribosomes read along mRNA, generating proteins by polymerizing amino acids donated by transfer RNA (tRNA) molecules bearing an appropriate anticodon.
Infections
Published in Evelyne Jacqz-Aigrain, Imti Choonara, Paediatric Clinical Pharmacology, 2021
Evelyne Jacqz-Aigrain, Imti Choonara
The Human Inmmunodeficiency Virus (HIV) is a retrovirus. The virus contains 2 identical copies of a positive sense (i.e. mRNA) single-stranded RNA strand about 9,500 nucleotides long. These may be linked to each other to form a genomic RNA dimer. The RNA dimer is in turn associated with a basic nucleocapsid (NC) protein (p9/6). The ribonucleoprotein particle is encapsidated by a capsid made up of a capsid protein (CA), p24. The capsid environment also contains other viral proteins such as integrase and reverse transcriptase. It also contains a wide variety of other macromolecules derived from the cell including tRNAlys3, which serves as a primer for reverse transcription. The capsid has an icosahedral structure. The capsid is in turn encapsidated by a layer of matrix protein (MA), p17. This matrix protein is associated with a lipid bilayer or envelope.
Nonhistone Nuclear Phosphoproteins
Published in Lubomir S. Hnilica, Chromosomal Nonhistone Proteins, 2018
The presence of the highly phosphorylated fraction of nuclear proteins in chromatin suggested to the early workers in the field that these proteins are involved with the regulation of transcription.7–9 Subsequently, numerous studies revealed that in addition to being in chromatin, protein-bound phosphate is present in virtually all subcomponents of the nucleus. For example phosphorylated proteins have been found in hnRNP (heterogeneous nuclear ribonucleoprotein) particles and nuclear envelope lamina.10–12 Therefore, additional roles such as transport of gene products, RNP assembly, and regulation of nuclear substructure throughout the cell cycle should be included in the list of nuclear phosphoprotein function.
Comparison of proteomic profiles from the testicular tissue of males with impaired and normal spermatogenesis
Published in Systems Biology in Reproductive Medicine, 2021
Jiaying Liang, Yichun Zheng, Weihong Zeng, Liuqing Chen, Shaofen Yang, Peng Du, Yujiang Wang, Xingsu Yu, Xiqian Zhang
Furthermore, HNRNPU protein is an abundant nucleoplasmic phosphoprotein (Kiledjian et al. 1992). It has been reported that cytoplasmic HNRNPU plays a role in the stability control of mRNA (Yugami et al. 2020) and the nuclear matrix protein HNRNPU was complexed in vivo with the glucocorticoid receptor (Eggert et al. 1997). Fackelmayer et al. believed that HNRNPU might play a role in the organization of chromosomal DNA in addition to its suggested role in hnRNA metabolism (Fackelmayer et al. 1994). A global analysis of HNRNPU-dependent splicing by RNA-seq coupled with bioinformatic analysis of associated splicing signals concluded that splicing site selection occurs through modulating the core splicing machinery. HNRNPU has also been identified as a potent regulator of nuclear ribonucleoprotein particles in several gene expression pathways (Xiao et al. 2012). We verified the differential expression of a spliceosome protein HNRNPU through WB and IHC, and determined that it was downregulated in the testicular tissues of patients with spermatogenesis disorders, which was like previously found to play an important role in spermatogenesis by affecting the regulation of apoptosis, death, and growth of spermatogenic cells (Li et al. 2012).
Covid-19: a comprehensive review of a formidable foe and the road ahead
Published in Expert Review of Respiratory Medicine, 2020
Arafat Hussain, Suniti Yadav, Vijay Hadda, Tejas M Suri, Pawan Tiwari, Saurabh Mittal, Karan Madan, Anant Mohan
Coronaviruses are members of the family – Coronaviridae, order – Nidovirales. Ranging from 65 nm to 125 nm in diameter, these are the largest enveloped single-stranded RNA (27 to 31 Kb) viruses [21] that belongs to the β sub-group of the four known sub-groups, i.e. alpha (α), beta (β), gamma (γ), and delta (δ) [22]. The term ‘corona’ represents the crown-like spike glycoproteins on the viral surface. SARS-CoV-2 has typical coronavirus structure comprising four main structural proteins coded by the sub-genomic RNAs, the spike (S), membrane (M), envelope (E), and nucleocapsid (N) (Figure 1). Functionally, the trans-membrane S glycoprotein (~150 kDa) is responsible for attachment to receptors and entry into host cells [23]. The most abundant glycoprotein, M protein (~25–30 kDa) helps to maintain the curvature of the viral membrane [24]. The E protein (8–12 kDa) is a small membrane protein involved in viral replication cycle viz. assembly, budding, envelope formation, release of virions, and pathogenesis [25]. The N protein (45 kDa) is a phosphoprotein that primarily functions to package the viral genome into a ribonucleoprotein particle to protect the genomic RNA and for incorporation into a viable virion [26].
How does an RNA selfie work? EV-associated RNA in innate immunity as self or danger
Published in Journal of Extracellular Vesicles, 2020
Yu Xiao, Tom Driedonks, Kenneth W. Witwer, Qian Wang, Hang Yin
In contrast with DNA, which is predominantly nuclear in healthy eukaryotic cells and thus constitutes a danger signal when found outside the cell, RNA molecules are found throughout the cell and are routinely released as extracellular RNA (exRNA) even in the healthy individual. The various exRNA carriers (EVs, lipoprotein particles, and ribonucleoprotein particles) have aroused considerable interest in recent years [11], but especially EVs because they are released without cell death and can reveal the health status of the cell of origin. Since exRNAs are released from all cells, these endogenous RNAs do not seem like good candidates as DAMPs. Yet a groundbreaking study of exRNA and innate immune signalling showed that certain host microRNAs could stimulate TLRs in the endosomal system [6]. This interesting finding, now repeatedly confirmed for miRNAs, at least, raises some important questions. How, exactly, is endogenous exRNA recognized as a danger? What other RNAs (or other molecules) might be involved in such signalling, and how? Despite a decade of study, these pressing questions have been answered only incompletely. However, numerous new examples of seemingly “nondanger” molecules have emerged, along with ideas about how they are recognized as abnormal (summarized in Figure 1).