Nuclear matrix

The exact function of this structure is still disputed, and its very existence has been called into question. Evidence for such a structure was recognised as long ago as 1948, and consequently many proteins associated with the matrix have been discovered. The presence of intra-cellular proteins is common ground, and it is agreed that proteins such as the Scaffold, or Matrix Associated Proteins (SAR or MAR) have some role in the organisation of chromatin in the living cell. There is evidence that the nuclear matrix is involved in regulation of gene expression in Arabidopsis thaliana.

Whenever a similar structure can actually be found in living cells remains a topic of discussion. According to some sources, most, if not all proteins found in nuclear matrix are the aggregates of proteins of structures that can be found in the nucleus of living cells. Such structures are nuclear lamina, which consist of proteins termed lamins which can be also found in the nuclear matrix.

Validity of nuclear matrix

For a long time the question whether a polymer meshwork, a "nuclear matrix" or "nuclear-scaffold" or "NuMat" is an essential component of the in vivo nuclear architecture has remained a matter of debate. While there are arguments that the relative position of chromosome territories (CTs), the equivalent of condensed metaphase chromosomes at interphase, may be maintained due to steric hindrance or electrostatic repulsion forces between the apparently highly structured CT surfaces, this concept has to be reconciled with observations according to which cells treated with the classical matrix-extraction procedures maintain defined territories up to the point where a minor subset of acidic nuclear matrix proteins is released – very likely those proteins that governed their association with the nuclear skeleton. The nuclear matrix proteome consists of structural proteins, chaperones, DNA/RNA-binding proteins, chromatin remodeling and transcription factors. The complexity of NuMat is an indicator of diverse structural and functional significance of its proteins.