Sequence complexity and diversity of polyadenylated RNA molecules of human normal resting, PHA-stimulated and leukemic lymphocytes.

The abundance and complexity of total poly(A)+RNA of human normal unstimulated lymphocytes, PHA-stimulated and leukemic lymphocytes were examined using the cDNA-poly(A)+ RNA hybridization technique. It was found that in both PHA-stimulated and leukemic lymphocytes the complexity of total poly(A)+RNA is strongly reduced in respect to normal unstimulated lymphocytes. The differences is due to a small portion, by weight, of high complexity sequences, suggesting the involvement or nuclear, not necessarily transcriptional, events. Moreover the heterologous hybridizations show that: 1) in PHA-stimulated lymphocytes there is a set of highly abundant sequences which are represented in normal and leukemic lymphocytes at a very reduced rate; 2) the sequences abundant in normal unstimulated lymphocytes are less represented in leukemic lymphocytes; the converse also is true, but at a lower extent. On the basis of available data, it is suggested that the observed changes in the abundance pattern of PHA-stimulated lymphocytes may be related mainly to a difference in the half-life of the mRNAs, while those of leukemic lymphocytes require some transcriptional or post-transcriptional nuclear event.