Herpesviridae
Erskine L. Palmer, Mary Lane Martin in Electron Microscopy in Viral Diagnosis, 2019
Herpes simplex virus was the first animal virus to be studied by negative stain electron microscopy (EM). In micrographs of thin sections, a herpesvirus capsid measuring about 100 nm can be clearly resolved. The herpesviruses of importance in medicine are herpes simplex virus types 1 and 2, varicella zoster virus, Epstein-Barr virus, cytomegalovirus, human B cell lymphotropic virus, and herpes simiae. Herpesvirus enters the cell by a process similar to pinocytosis or by fusion with the cell. The exact process by which herpesvirus is released from the cell is not clear. However, particles appear to accumulate between the inner and outer lamella of the nuclear membrane or in the endoplasmic reticulum. EM has made an important contribution to the rapid diagnosis of herpesviruses from vesicular fluids, urine, and brain biopsy specimens. There is also some evidence that herpesviruses have a middle capsid layer just beneath the capsid and an inner capsid about 45 nm in diameter which encloses the core.
Post-transcriptional Regulation
David S. Latchman in Gene Control, 2020
The transcription of DNA into RNA represents the first stage in the process of gene expression and is the major control point regulating which genes are expressed. Following initiation of the primary RNA transcript, transcription proceeds by the progressive addition of ribonucleotides to the RNA chain so that an RNA molecule is produced with bases complementary to those present in the DNA being transcribed. The RNA transcript is therefore modified at both ends, firstly by capping at the 5' end and subsequently by cleavage and polyadenylation at the 3' end. The dual role of C-terminal domain phosphorylation in transcriptional elongation and processing of the RNA transcript therefore couples the two events, ensuring that the elongating RNA transcript is correctly processed. The processed RNA must therefore be transported through the nuclear membrane from the nucleus to the cytoplasm before it can be translated into protein.
Cell-medicated gene transfer
R.M. Twyman in Gene Transfer to Animal Cells, 2004
Many different animal viruses have been exploited as vectors, mostly for foreign gene expression in cultured cells but also for gene transfer in vivo . Novel strategies involving site-specific recombination and transposition have also been used to generate recombinant viruses. The large genome size and unusual replication strategy represent major obstacles to the design and construction of expression vectors. The wild-type genome has two genes, one encoding viral replicase and the other encoding a self-cleaving polyprotein containing all the capsid structural proteins. The adenovirus fiber proteins have the ability to disrupt the endosome, releasing the naked capsid into the cytoplasm where it is transported to the nuclear membrane. The transfection of recombinant RNA into cells is unsuitable for certain experiments, especially for gene delivery in vivo . The chapter concludes with a short discussion about the potential of combining certain features of different viruses to make them more suitable vectors.
A novel anemia associated with membranous cytoplasm degeneration in 16 patients: an ultrastructural study
Published in Ultrastructural Pathology, 2018
Yong-Xin Ru, Shu-Xu Dong, Yuan Li, Shi-Xuan Zhao, Hao-yue Liang, Xiao-fan Zhu, Yi-zhou Zheng, Feng-kui Zhang
Sixteen patients with mild anemia and hemolysis were difficult to be classified into any known category based on laboratory examinations and light microscopy. To make a definite diagnosis and investigate the pathomechanism, ultrastructural study was performed on erythroid cells from 16 patients. Transmission electron microscopy demonstrated a series of alterations of cytoplasm, including cytoplasm sequestration, membranous transformation, and degeneration in erythroblasts and reticulocytes at different stages. The affected erythroblasts were usually complicated with chromatin condensation, karyorrhexis, nuclear membrane lysis, and megaloblastic changes. The reticulocytes with the cytoplasm alterations had a huge size from 10 um to 15 um in diameter. The membranous cytoplasm degeneration revealed a unique pathomechanism of dyserythropoiesis and ineffective erythropoiesis in 16 patients with anemia, and suggested a novel anemia category though more details remained to be investigated.
Role of intranuclear lipids in health and disease
Published in Clinical Lipidology, 2011
The nuclear lipid fraction is comprised of glycerophospholipids, sphingolipids, plasmalogens, gangliosides, cholesterol and fatty acids. Intranuclear lipid enzymes are responsible for their active metabolism completely independently from that of other cell membranes. The crosstalk between glycerophospholipids and sphingolipids controls the nuclear lipid mediators such asceramide and diacylglycerol that are in equilibrium when the cells are resting and change whenthe cells are stimulated. This article focuses on the characteristics, localization and metabolism of intranuclear lipids. This article describes the examples of their function that have been discovered so far and an additional function, which has emerged from recent insights; somelipids associated with the inner nuclear membrane are organized to form a platform for DNA duplication and transcription that could play a role in health and disease.
Novel insights into the disease etiology of laminopathies
Published in Rare Diseases, 2013
Chin Yee Ho, Diana E Jaalouk, Jan Lammerding
Laminopathies are a heterogeneous group of diseases that are caused by mutations in the nuclear envelope proteins lamins A and C. Laminopathies include dilated cardiomyopathy, Emery-Dreifuss muscular dystrophy, and familial partial lipodystrophy. Despite their near-ubiquitous expression, most laminopathies involve highly tissue-specific phenotypes, often affecting skeletal and cardiac muscle. The underlying mechanism(s) remain incompletely understood. We recently reported that altered actin dynamics in lamin A/C-deficient and mutant cells disturb nuclear shuttling of the transcriptional co-activator MKL1, which is critical for cardiac function. Expression of the inner nuclear membrane protein emerin rescues MKL1 translocation through modulating actin dynamics. Here, we elaborate on these findings, discuss new insights into the role of nuclear actin in MKL1activity, and demonstrate that primary human skin fibroblasts from a patient with dilated cardiomyopathy have impaired MKL1 nuclear translocation. These findings further strengthen the relevance of impaired MKL1 signaling as a potential contributor to the disease mechanism in laminopathies.
Related Knowledge Centers
- Organelles
- Cell Nucleus
- Endoplasmic Reticulum
- Plastids
- Vacuoles
- Intracellular Membranes
- Cell Membrane Structures