[Association of DNA with the nuclear skeleton]

A significant functional role is ascribed to DNA association with the nuclear skeleton. Specific proteins tightly bound to DNA have been discovered. According to one point of view these proteins perform constant attachment of DNA to the nuclear matrix, however, according to other authors this complex exists in transcribed genes only. In proliferating cell DNA is anchored by DNA-topoisomerase II and DNA-polymerase alpha. Except for proteins this function is performed by glycoproteins, neutral and phospholipids, RNA. Three types of specific DNA sequences have been elucidated: 1. AT-rich enhancers (SAR); 2. GC-rich origins of replication; 3. centromere and satellite DNA. In places of binding to the nuclear matrix DNA bears the numerous defects of secondary structure. Based on different criteria several types of DNA complexes with nuclear matrix proteins are distinguished: 1. resistant (lamina) and sensitive (intramolecular fibrils) to chelating agents; 2. formed by transcriptional complexes (transitory) and origins of replication (constant); 3. tight (resistant to salt-urea solutions, formed by replicative complex proteins) and weak (sensitive).