Anti-CBX6 monoclonal antibody Made to order

The establishment and maintenance of mammary epithelial cell identity depends on the activity of a group of proteins, collectively called maintenance proteins, that act as epigenetic regulators of gene transcription through DNA methylation, histone modification, and chromatin remodeling. Increasing evidence indicates that dysregulation of these crucial proteins may disrupt epithelial cell integrity and trigger breast tumor initiation. Therefore, we explored in silico the expression pattern of a panel of 369 genes known to be involved in the establishment and maintenance of epithelial cell identity and mammary gland remodeling in cell subpopulations isolated from normal human mammary tissue and selectively enriched in their content of bipotent progenitors, committed luminal progenitors, and differentiated myoepithelial or differentiated luminal cells. The results indicated that, compared to bipotent cells, differentiated myoepithelial and luminal subpopulations were both characterized by the differential expression of 4 genes involved in cell identity maintenance: CBX6 and PCGF2, encoding proteins belonging to the Polycomb group, and SMARCD3 and SMARCE1, encoding proteins belonging to the Trithorax group. In addition to these common genes, the myoepithelial phenotype was associated with the differential expression of HDAC1, which encodes histone deacetylase 1, whereas the luminal phenotype was associated with the differential expression of SMARCA4 and HAT1, which encode a Trithorax protein and histone acetylase 1, respectively. The luminal compartment was further characterized by the overexpression of ALDH1A3 and GATA3, and the down-regulation of NOTCH4 and CCNB1, with the latter suggesting a block in cell cycle progression at the G(2) phase. In contrast, myoepithelial differentiation was associated with the overexpression of MYC and the down-regulation of CCNE1, with the latter suggesting a block in cell cycle progression at the G(1) phase.

Background: Polycomb group (PcG) proteins maintain expression pattern of genes set early during development. Although originally isolated as regulators of homeotic genes, PcG members play a key role in epigenetic mechanism that maintains the expression state of a large number of genes. Polycomb (PC) is conserved during evolution and while invertebrates have one PC gene, vertebrates have five or more homologues. It remains unclear if different vertebrate PC homologues have distinct or overlapping functions. We have identified and compared the sequence of PC homologues in various organisms to analyze similarities and differences that shaped the evolutionary history of this key regulatory protein. Results: All PC homologues have an N-terminal chromodomain and a C-terminal Polycomb Repressor box. We searched the protein and genome sequence database of various organisms for these signatures and identified similar to 100 PC homologues. Comparative analysis of these sequences led to the identification of a novel insect specific motif and several novel and signature motifs in the vertebrate homologue: two in CBX2 (Cx2.1 and Cx2.2), four in CBX4 (Cx4.1, Cx4.2, Cx4.3 and Cx4.4), three in CBX6 (Cx6.1, Cx6.2 and Cx6.3) and one in CBX8 (Cx8.1). Additionally, adjacent to the chromodomain, all the vertebrate homologues have a DNA binding motif -AT-Hook in case of CBX2, which was known earlier, and 'AT-Hook Like' motif, from this study, in other PC homologues. Conclusion: Our analysis shows that PC is an ancient gene dating back to pre bilaterian origin that has not only been conserved but has also expanded during the evolution of complexity. Unique motifs acquired by each homologue have been maintained for more than 500 millions years indicating their functional relevance in boosting the epigenetic 'tool kit'. We report the presence of a DNA interaction motif adjacent to chromodomain in all vertebrate PC homologues and suggest a three-way 'PC-histoneH3-DNA' interaction that can restrict nucleosome dynamics. The signature motifs of PC homologues and insect specific motif identified in this study pave the way to understand the molecular basis of epigenetic mechanisms.