Immunological assay of double-helical segments in RNA fractions of different molecular size extracted from acute myeloid leukemia blast cells.

Whole-cell RNA, extracted from acute myeloid leukemia blast cells, was fractionated by sedimentation through sucrose gradients. The proportion of double-helical segments present in each fraction was then determined by a quantitative microcomplement fixation assay that specifically measures double-helical RNA. Sizable amounts of double-helical segments were detected in all fractions of cellular RNA corresponding to S values higher than approximately 20. In all cell populations examined the highest proportion of double-helical segments was found in RNA fractions sedimenting faster then the 45 S ribosomal precursors RNA, i.e., in fractions including only heterogeneous nuclear RNA.