Characterization, expression and subcellular distribution of a novel MFP1 (matrix attachment region-binding filament-like protein 1) in onion

• Published in: Protoplasma 2008-09, Vol.233 (1-2), p.31-38
• Main Authors: Samaniego, R, de la Torre, C, Moreno Díaz de la Espina, S
• Format: Article
• Language: English
• Subjects: Allium cepa; Biomedical and Life Sciences; Cell Biology; Cell Cycle; Cell Nucleus - metabolism; Cell Nucleus - ultrastructure; Cell Proliferation; Chloroplast; Chloroplasts - metabolism; Confocal and electron microscopy; Euchromatin; Immune Sera; Life Sciences; Matrix Attachment Region Binding Proteins - metabolism; Meristem - cytology; Meristem - metabolism; Meristem - ultrastructure; MFP1 protein; Molecular Weight; Nucleus; Onions - cytology; Onions - metabolism; Plant Leaves - cytology; Plant Leaves - metabolism; Plant Proteins - metabolism; Plant Sciences; Protein Transport; Proteins; Subcellular Fractions - metabolism; Zoology
• ISSN: 0033-183X; 1615-6102
• DOI: 10.1007/s00709-008-0308-9

MFP1 (matrix attachment region-binding filament-like protein 1) is a conserved nuclear and chloroplast DNA-binding protein encoded by a nuclear gene, well characterized in dicot species. In monocots, only a 90 kDa MFP1-related protein had been characterized in the nucleus and nuclear matrix of Allium cepa proliferating cells. We report here a novel MFP1-related nuclear protein of 80 kDa in A. cepa roots, with Mr and pI values similar to those of MFP1 proteins in dicot species, and which also displays a dual location, in the nucleus and chloroplasts of leaf cells. However, this novel protein is not a nuclear matrix component. It shows a spotted intranuclear distribution in small foci differing from the nuclear bodies containing the 90 kDa protein. In electron microscopy analysis, the intranuclear foci containing the 80 kDa MFP1 appeared as small loose structures at the periphery of condensed chromatin patches. This protein was also located in the nucleolus. It was abundant in meristematic cells, but its level fell when proliferation stopped. This different expression and distribution, and its preferential location at the boundaries between heterochromatin and euchromatin, suggest that the novel 80 kDa protein might be associated with decondensed DNA and could play a role in chromatin organization.