Nuclear envelope influences on cell-cycle progression

Characterization of lamin B receptor of Sf9 cells and its fate during Autographa californica nucleopolyhedrovirus infection

Baculovirus nucleocapsids egress from the nuclear membrane during infection. However, details of alternation of nuclear membrane structure during baculovirus egress are unknown. In this study, we examined the changes of lamin B receptor (LBR), a main inner nuclear membrane component, during Autographa californica nucleopolyhedrovirus (AcMNPV) infection. Firstly, the open reading frame (Orf) of Sf9 lbr was cloned by reverse transcription PCR, and the distribution of LBR in Sf9 cells were observed by fusing LBR with the red fluorescence protein mcherry. Besides, the amount of endogenous LBR during AcMNPV infection was detected by western blotting. Moreover, the distribution of LBR after AcMNPV infection was observed under the confocal fluorescence microscopy. Furthermore, the effects of protein kinase C (PKC) inhibitor on stability of LBR and release of budded virus (BVs) were determined. The results showed that Sf9 lbr contains an Orf of 2040 nucleotides (NTs), which encodes a predicted protein of 679 amino acids (AAs). Fluorescence microscopy showed that LBR is localized to the nuclear membrane. Western blotting result showed that the amount of endogenous LBR is significantly reduced after AcMNPV infection. Transfection and infection assay demonstrated that the fluorescence of LBR nearly completely disappeared after viral infection. PKC inhibitor can suppress the degradation of LBR induced by AcMNPV, resulting in the reduction of viral titer of progeny viruses. The electron microscopy analysis demonstrated that PKC inhibitor did not influence virion entry, uncoating, and assembly, but may partially protect the nuclear membrane from disruption by AcMNPV. Taken together, AcMNPV infection can distort the expression of LBR, which may promote the egress of nucleocapsids.

Breaking the scale: how disrupting the karyoplasmic ratio gives cancer cells an advantage for metastatic invasion

Nuclear size normally scales with the size of the cell, but in cancer this 'karyoplasmic ratio' is disrupted. This is particularly so in more metastatic tumors where changes in the karyoplasmic ratio are used in both diagnosis and prognosis for several tumor types. However, the direction of nuclear size changes differs for particular tumor types: for example in breast cancer, larger nuclear size correlates with increased metastasis, while for lung cancer smaller nuclear size correlates with increased metastasis. Thus, there must be tissue-specific drivers of the nuclear size changes, but proteins thus far linked to nuclear size regulation are widely expressed. Notably, for these tumor types, ploidy changes have been excluded as the basis for nuclear size changes, and so, the increased metastasis is more likely to have a basis in the nuclear morphology change itself. We review what is known about nuclear size regulation and postulate how such nuclear size changes can increase metastasis and why the directionality can differ for particular tumor types.

Physiological and Pathological Aging Affects Chromatin Dynamics, Structure and Function at the Nuclear Edge

Lamins are intermediate filaments that form a complex meshwork at the inner nuclear membrane. Mammalian cells express two types of Lamins, Lamins A/C and Lamins B, encoded by three different genes, LMNA, LMNB1, and LMNB2. Mutations in the LMNA gene are associated with a group of phenotypically diverse diseases referred to as laminopathies. Lamins interact with a large number of binding partners including proteins of the nuclear envelope but also chromatin-associated factors. Lamins not only constitute a scaffold for nuclear shape, rigidity and resistance to stress but also contribute to the organization of chromatin and chromosomal domains. We will discuss here the impact of A-type Lamins loss on alterations of chromatin organization and formation of chromatin domains and how disorganization of the lamina contributes to the patho-physiology of premature aging syndromes.

ATR-mediated regulation of nuclear and cellular plasticity

ATR (Ataxia Telangiectasia and Rad3-related) is a member of the Phosphatidylinositol 3-kinase-related kinases (PIKKs) family, amongst six other vertebrate proteins known so far. ATR is indispensable for cell survival and its essential role is in sensing DNA damage and initiating appropriate repair responses. In this review we highlight emerging and recent observations connecting ATR to alternative roles in controlling the nuclear envelope, nucleolus, centrosome and other organelles in response to both internal and external stress conditions. We propose that ATR functions control cell plasticity by sensing structural deformations of different cellular components, including DNA and initiating appropriate repair responses, most of which are yet to be understood completely.

Emerging common molecular pathways for primary dystonia

The dystonias are a group of hyperkinetic movement disorders whose principal cause is neuron dysfunction at 1 or more interconnected nodes of the motor system. The study of genes and proteins that cause familial dystonia provides critical information about the cellular pathways involved in this dysfunction, which disrupts the motor pathways at the systems level. In recent years study of the increasing number of DYT genes has implicated a number of cell functions that appear to be involved in the pathogenesis of dystonia. A review of the literature published in English-language publications available on PubMed relating to the genetics and cellular pathology of dystonia was performed. Numerous potential pathogenetic mechanisms have been identified. We describe those that fall into 3 emerging thematic groups: cell-cycle and transcriptional regulation in the nucleus, endoplasmic reticulum and nuclear envelope function, and control of synaptic function. © 2013 Movement Disorder Society.

Nuclear envelope disease and chromatin organization

The fifth U.K. meeting on nuclear envelope disease and chromatin brought together international experts from across the field of nuclear envelope biology to discuss the advancements in a class of tissue-specific degenerative diseases called the laminopathies. Clinically, these range from relatively mild fat-wasting disorders to the severe premature aging condition known as Hutchinson-Gilford progeria syndrome. Since the first association of the nuclear envelope with human inherited disease in 1994, there has been an exponential increase in an unexpected variety of functions associated with nuclear envelope proteins, ranging from mechanical support and nucleocytoskeletal connections to regulation of chromatin organization and gene expression. This Biochemical Society Focused Meeting reinforced the functional complexity of nuclear-associated diseases, revealed new avenues to be investigated and highlighted the signalling pathways suitable as therapeutic targets.