The nuclear protein p30 specifically interacts with a nuclear matrix attachment region from the rat genome.

In our previous study, a 454 bp DNA fragment was isolated from rat genomic DNA as an element which interacts with nuclear matrix proteins, i.e. a Matrix Associated Region (MAR). Computer analyses revealed that the right half of this fragment, named RME (Rat MAR Element), possesses a high matrix association potential and is likely to be responsible for the matrix association of the whole sequence. RME was used as a probe in an electrophoretic mobility shift assay (EMSA), and with the use of Southwestern blotting, a rat liver nuclear protein which binds specifically to it was identified. Its molecular mass was estimated by SDS-PAGE as 30 kDa (p30). Polyclonal antibodies raised against protein-RME complexes caused a super-shift of specific complexes in EMSA, and bound to p30 in nuclear extracts of rat liver in Western blotting. The immunofluorescence labelling of a rat embryonic fibroblast cell monolayer with anti-p30 antibody revealed a mainly intranuclear pattern of staining.