Rev‐dependent association of the intron‐containing HIV‐1 gag mRNA with the nuclear actin bundles and the inhibition of its nucleocytoplasmic transport by latrunculin‐B

Abstract

Background: A hallmark of HIV-1 gene expression is that unspliced genomic RNA, which also acts as mRNA for the expression of Gag/Pol, is exported to the cytoplasm. Rev directs this transport through the nuclear export signal (NES).

Direct actin binding to A- and B-type lamin tails and actin filament bundling by the lamin A tail

“…The first site, AB-1, is shared and conserved in all lamins whereas the second site, AB-2, is unique to lamin A. F-actin bundles were detected by rhodamine-phalloidin labeling and by TEM imaging, suggesting lamin-mediated bundling was not an artifact of centrifugation in the high-and low-speed pelleting assays. These findings suggest potential concerted mechanisms for pathways that are known to require both polymerizable actin and A-type lamins, such as mRNA export, [36][37][38][39] intranuclear chromatin movement 40,41 and transcription. 5,[42][43][44] Although nuclei lack phalloidin-stainable F-actin, approximately 20% of actin in the nucleus is found in alternative polymeric state(s).…”

Stress Activation of Mammary Epithelial Cell Xanthine Oxidoreductase Is Mediated by p38 MAPK and CCAAT/Enhancer-binding Protein-β

“…D, the densitometric scan is shown. Protein loading for both cytoplasmic and nuclear Western blots was normalized to ␤-actin as described (33). E, HC11 cells were transfected with 1.0 g of the cDNA expression clone for p38␣ and the indicated concentrations of the pMKK6bE expression clone, and EMSA analysis was performed on nuclear and cytoplasmic fractions using the mouse XOR Ϫ140/Ϫ170 C/EBP␤ oligonucleotide.…”

Establishment of latrunculin-A resistance in HeLa cells by expression of R183A D184A mutant β-actin

“…Oncogene (2003Oncogene ( ) 22, 627-631. doi:10.1038 Actin plays central roles in cell motility processes such as cytokinesis, cell locomotion, exocytosis and endocytosis through formation of the actin cytoskeleton (Mitchson and Cramer, 1996). Recently, the possibility that actin also functions in the cell nucleus, probably mainly in monomer form (Zhao et al, 1998;Kimura et al, 2000;Rando et al, 2000;Wasser and Chia, 2000), has been emerging. For example, b-actin monomer has been suggested to be a functional component of the mammalian SWI/SNF-like BAF complex (Zhao et al, 1998).…”

“…For example, b-actin monomer has been suggested to be a functional component of the mammalian SWI/SNF-like BAF complex (Zhao et al, 1998). It has also been suggested that nuclear b-actin bundles may be involved in the HIV Rev-dependent regulation of nucleocytoplasmic transport of viral mRNA (Kimura et al, 2000). To dissect its dynamics and functions, several actin-disrupting drugs have been widely and effectively employed.…”

“…However, it remains controversial as to whether all of the various phenotypes observed with latrunculin treatment in mammalian cells more complicated than yeast are truly the consequence of its specific actions against actin. For example, the concentrations of latrunculin-B required for inhibiting the DNA-dependent ATPase activity of the BAF complex or the specific nucleocytoplasmic transport of HIV mRNA appear very high, as compared with that disrupting cytoplasmic actin filaments (Zhao et al, 1998;Kimura et al, 2000). Also, it has yet to be clarified why receptor-mediated endocytosis or neurotransmitter release, both of which are suggested to be regulated by actin, are affected by latrunculin-A but not by cytochalasin-D (Lamaze et al, 1997;Morales et al, 2000).…”