Regulation Of Cell-specific Expression Research Articles

Histone deacetylases 1 and 2 are required for brain development.

Epigenetic modifications of histones have been implicated in the regulation of cell specific expression of genes required for neuronal development. The best studied post-translational (epigenetic) modification of histones is the process of reversible acetylation. Two types of enzymes - histone acetyltransferases (HATs) and histone deacetylases (HDACs) establish and maintain specific patterns of histone acetylation in balance, thereby contributing to both transcriptional activation and repression of specific sets of genes. Histone deacetylases catalyze the removal of acetyl groups from selected lysine residues in the conserved tails of core histone proteins and are considered as transcriptional corepressors. A significant amount of data implicates HDACs in diverse biological processes, including tissue specific developmental program by silencing specific growth-inhibitory genes. In line with this, gene disruption studies have shown that the class I deacetylases, HDAC1 and HDAC2 play an essential role in nervous system development. In the present review, we briefly highlight current insights supporting the function of histone deacetylases in rodent brain development and discuss present knowledge referring to their role in neurogenesis, taking into consideration results obtained in culture systems and in in vivo studies.

Regulation of cell specific expression of calcyclin (S100A6) in nerve cells and other tissues

Many of the small, acidic, calcium binding S 100 proteins present in the brain specifically map different anatomical regions and cell types and their overexpression is implicated in pathological changes. Similarly to other members of the S100 protein family, calcyclin (S100A6) is expressed in a cell specific manner and is found in subpopulations of neurons and astrocytes in the brain and in epithelial cells and fibroblasts. In this article we review data concerning the cell specific expression of S100 protein genes and present experimental results on the regulation of the calcyclin gene. We have performed promoter deletion studies to locate regions within the calcyclin gene promoter responsible for transcriptional regulation. The results demonstrate that the 3 kb long calcyclin gene promoter lacks a cell specific cis-acting element and drives the expression of the reporter gene also in cells that do not express endogenous calcyclin. The expression is modulated by positive and negative elements acting uniformly in the four different cell lines studied. The first intron of the calcyclin gene was found to have an inhibitory influence on expression regardless of cell type. It was also shown that calcyclin expression can be induced in calcyclin-negative cells by treatment with 5-azacytidine suggesting the involvement of gene methylation in its cell specific expression. The results are discussed in light of the data available on the regulation of other S100 genes.