Organization of the lamin scaffold in the internal nuclear matrix of normal and transformed hepatocytes |
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Authors: | Paola Barboro Erica Repaci Cecilia Balbi |
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Institution: | a Istituto Nazionale per la Ricerca sul Cancro, Largo Rosanna Benzi, 10-16132 Genova, Italy b CNR, Istituto per lo Studio delle Macromolecole, ISMAC-Genova, Via De Marini, 6-16149 Genova, Italy |
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Abstract: | Nuclear lamins are among the more abundant proteins making up the internal nuclear matrix, but very little is known about their structure in the nucleoplasm. Using immunoelectron microscopy, we demonstrate the organization of lamins in the nuclear matrix isolated from rat hepatocytes for the first time. Lamin epitopes are arrayed both in locally ordered clusters and in quasi-regular rows. Fourier filtering of the images demonstrates that the epitopes are placed at the nodes and halfway between the nodes of square or rhombic lattices that are about 50 nm on each side, as well as along rows at regular ∼25-nm intervals. In addition, we have compared this structure with that of the internal nuclear matrix isolated from persistent hepatocyte nodules. In transformed hepatocytes, the islands of lamin lattice are lost, and only a partial regularity in the rows of gold particles remains. We suggest that orthogonal lattice assembly might be an intrinsic property of lamin molecules, and that the disassembly may be triggered by simple molecular events such as phosphorylation. |
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Keywords: | NM nuclear matrix MARs matrix attachment regions INM internal nuclear matrix NuMA nuclear mitotic apparatus protein hnRNP heterogeneous nuclear ribonucleoprotein NH normal Hepatocytes PHN persistent hepatocyte nodules VRC vanadyl ribonucleoside complex BI binary image FFT fast Fourier transform |
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