MAF1, a novel plant protein interacting with matrix attachment region binding protein MFP1, is located at the nuclear envelope

The interaction of chromatin with the nuclear matrix via matrix attachment region (MAR) DNA is considered to be of fundamental importance for chromati n organization in all eukaryotic cells. MAR binding filament-like protein 1 (MFP1) from tomato is a novel plant protein that specifically binds to MAR DNA, Its filament protein-like structure makes it a likely candidate for a structural component of the nuclear matrix. MFP1 is located at nuclear mat rix-associated, specklelike structures at the nuclear envelope. Here, we re port the identification of a novel protein that specifically interacts with MFP1 in yeast two-hybrid and in vitro binding assays. MFP1 associated fact or 1 (MAF1) is a small, soluble, serine/threonine-rich protein that is ubiq uitously expressed and has no similarity to known proteins. MAF1, like MFP1 , is located at the nuclear periphery and is a component of the nuclear mat rix. These data suggest that MFP1 and MAF1 are in vivo interaction partners and that both proteins are components of a nuclear substructure, previousl y undescribed in plants, that connects the nuclear envelope anti the intern al nuclear matrix.