Discrete and heterogeneous high molecular weight RNAs complementary to a long dispersed repeat family (a possible transposon) of human DNA.

Approximately 1% of heterogeneous nuclear RNA and approximately 0.035% of cytoplasmic RNA from a cultured line of human lymphoblastoid cells is complementary to a long dispersed repetitious sequence that comprises at least 6% of human DNA. The complementary nuclear RNA is both heterogeneously and discretely sized and is present in both poly(A)-terminated and non-poly(A)-terminated molecules. The complementary cytoplasmic RNA is mainly in discretely sized molecules ranging in size from approximately 600 to 8200 bases, some of which are most abundantly represented in poly(A)-terminated molecules, whereas others are most abundantly represented in non-poly(A)-terminated molecules. Few, if any, of the complementary cytoplasmic RNAs can be found associated with polyribosomes. The dispersed repeat sequence exhibits substantial restriction enzyme fragment length polymorphisms in human DNA and is also present in mouse DNA, although some regions of the human repeat appear to be more abundantly represented in mouse DNA than are other regions.