Topology of repeated sequences: relationship of nuclear RNA to the repeated sequences of the main and satellite DNA in mouse plasmocytoma cells.

The topology of repeated sequences in mouse plasmocytoma DNA was studied by high-resolution CsCl density gradient centrifugation and heterogeneous nuclear RNA.DNA hybridization. Satellite region DNA of plasmocytoma cells contains additional components and hybridizes specifically with entire heterogeneous nuclear RNA molecules. A linkage is demonstrated between the A+T-rich satellite sequences and those hybridizing with heterogeneous nuclear RNA. Heavy DNA also hybridizes specifically with heterogeneous nuclear RNA molecules that show sequence similarity to heterogeneous nuclear RNA hybridized to satellite DNA. These results could suggest that part of satellite DNA became heavier after integration of some other DNA species, which could belong to a virus or to immunoglobulin repetitive genes. Dispersed, highly repetitive, short nucleotide sequences could constitute recognition sites for such a process.