Nuclear subcompartments: an overview.

The advance in biochemical and microscopy techniques has revealed the complexity and intricate nucleoplasm structure. Several subcompartments were identified in nucleus and the importance of these subcompartments in processes crucial for normal nuclear activity has been demonstrated. In this mini-review, we will give an overview about the composition, function, and importance of the major nuclear subcompartments. Also, we will show the impact that perturbing these structures can cause in normal nuclear activity, and how these can contribute to the development of some human diseases.

Iron-induced oxidative stress up-regulates calreticulin levels in intestinal epithelial (Caco-2) cells.

Calreticulin, a molecular chaperone involved in the folding of endoplasmic reticulum synthesized proteins, is also a shock protein induced by heat, food deprivation, and chemical stress. Mobilferrin, a cytosolic isoform of calreticulin, has been proposed to be an iron carrier for iron recently incoming into intestinal cells. To test the hypothesis that iron could affect calreticulin expression, we investigated the possible associations of calreticulin with iron metabolism. To that end, using Caco-2 cells as a model of intestinal epithelium, the mass and mRNA levels of calreticulin were evaluated as a function of the iron concentration in the culture media. Increasing the iron content in the culture from 1 to 20 microM produced an increase in calreticulin mRNA and a two-fold increase in calreticulin. Increasing iron also induced oxidative damage to proteins, as assessed by the formation of 4-hydroxy-2-nonenal adducts. Co-culture of cells with the antioxidants quercetin, dimethyltiourea and N-acetyl cysteine abolished both the iron-induced oxidative damage and the iron-induced increase in calreticulin. We postulate that the iron-induced expression of calreticulin is part of the cellular response to oxidative stress generated by iron.