Matrix attachment region binding protein MFP1 is localized in discrete domains at the nuclear envelope.
Recently, it has been suggested that nuclear processes, such as replication, transcription, and splicing, are spatially organized and associated with a nuclear framework called the nuclear matrix, a structure of unknown molecular composition. It has been shown that chromatin is attached to the nuclear matrix via specific DNA fragments called matrix attachment regions (MARs). We have begun to dissect the plant nuclear matrix by isolating a DNA binding protein with specific affinity for MARs. Here, it is shown that MAR binding filament-like protein 1 (MFP1) is associated with specklelike structures at the nuclear periphery that are part of isolated nuclei and the nuclear matrix. A predicted N-terminal transmembrane domain is necessary for the specific targeting of MFP1 to the speckles, indicating an association with the nuclear envelope-endoplasmic reticulum continuum. In addition, it is shown that a marker protein for plant microtubule organizing centers, which has been shown to be localized on the outside of the plant nuclear envelope, is also part of the nuclear matrix. These findings indicate a close and previously undescribed connection in plants between the nuclear envelope and the internal nuclear matrix, and they suggest a function for MFP1 in attaching chromatin to specific sites at the nuclear periphery.
Gindullis
F
F
DuPont Central Research and Development, P.O. Box 80402, Wilmington, Delaware 19880-0402, USA.
Meier
I
I
D029681:Arabidopsis Proteins; D001665:Binding Sites; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000032:analysis; D036961:Matrix Attachment Region Binding Proteins; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism*; D009685:Nuclear Envelope / Q000378:metabolism* / Q000648:ultrastructure; D015530:Nuclear Matrix / Q000378:metabolism* / Q000648:ultrastructure; D010940:Plant Proteins / Q000378:metabolism; D010947:Plants, Toxic; D011523:Protoplasts / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000032:analysis; D014026:Nicotiana; D014162:Transfection
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; C120563:MAR binding filament-like protein 1, Arabidopsis; D036961:Matrix Attachment Region Binding Proteins; D008565:Membrane Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins