Isolation of SDS-stable complexes of the intermediate filament protein vimentin with repetitive, mobile, nuclear matrix attachment region, and mitochondrial DNA sequence elements from cultured mouse and human fibroblasts

Crosslinkage of vimentin to DNA in mouse L929 cells by formaldehyde and iso lation of SDS-stable DNA-vimentin complexes from normal L929 cells and mous e and human embryo fibroblasts indicated close spatial relations between th ese components in the intact cell. The adducts, obtained by immunoprecipita tion with anti-vimentin antibody, contained substantial quantities, not onl y of repetitive and mobile sequence elements such as centromeric satellite DNA, telomere DNA, microsatellites and minisatellites, long and short inter spersed nucleotide elements, and retroposons, but also of mitochondrial (mt ) DNA. Because the SDS-stable complexes could be isolated with distinctly h igher yields from oxidatively stressed, senescent fibroblasts and were diss ociated by boiling, they possibly arose from accidental condensation reacti ons mediated by unsaturated and dialdehydes, products of free radical-induc ed lipid peroxidation. They can therefore be considered vestiges of a gener al interaction of vimentin with cellular DNA. The sequence patterns of thei r DNA fragments were similar to those of extrachromosomal circular and line ar DNA, including retroviral elements, markers and enhancers of genomic ins tability that also occur in the cytoplasm and are able to transport vimenti n into the nucleus. Many of the fragments were also remarkably similar to A T-rich nuclear matrix attachment regions (MARs) in that they contained, in addition to various mobile elements, a palette of typical MAR motifs. With its tendency to multimerize and to interact with single-stranded and superc oiled DNA, vimentin thus behaves like a nuclear matrix protein and may as s uch participate in a variety of nuclear matrix-associated processes such as replication, recombination, repair, and transcription of DNA. These activi ties seem to be extendible to the mitochondrial compartment, as vimentin wa s also crosslinked. to mtDNA, preferentially to its D-loop and hypervariabl e main control region. These sites are prone to point and deletion mutation s and, like nuclear MARs, are associated with the cyto-karyomatrix. Moreove r, as a developmentally regulated and tissue-specific cyto-karyomatrix prot ein, vimentin may contribute to the organization of chromatin, including ce ntromeric and telomeric heterochromatin at the nuclear periphery, with all its consequences for genomic activities during embryogenesis and in adultho od of vertebrates. However, because of its high affinity for hypervariable, recombinogenic DNA sequences, vimentin is proposed to play a major role in both the preservation and the evolution of the nuclear and mitochondrial g enome.