Nuclear retention of 18S ribosomal RNA by human myeloma cells.

Normal quiescent lymphocytes regulate their ribosome content by selectively degrading newly synthesized 18S ribosomal RNA. Unlike actively dividing HeLa cells, lymphocytes retain 18S ribosomal RNA in the nucleus after synthesis instead of immediately transporting it to the cytoplasm. Subcellular fractionation of the highly differentiated human neoplastic lymphocyte RPMI-8226 reveals that this cell line also retains 18S ribosomal RNA in the nucleus, a trait not displayed by the less differentiated human lymphoblastoid cell line RPMI-4265. These observations suggest that neoplastic cells can be phenotypically characterized by their ribosomal RNA processing patterns.