An analysis of cytoplasmic RNA populations in Drosophila melanogaster, Oregon R

Nucleic acid reassociation methods were used to estimate the number of different polyadenylated RNA [poly (A) + RNA] sequences in the cytoplasm of whole Drosophila melanogaster at different stages of development and in the cytoplasm of cells of the L3 cell line. The number-average length (LN) of poly (A) + RNA from L3 cells is 1.4 kb, and the steady-state LN of the poly (A) tracts is 70 nucleotides. Analysis of RNA-driven reassociation with copy DNA shows that the poly (A) + RNA from L3 cells contains 5200 different sequences distributed in three abundance classes. The RNA forms hybrid duplexes with about 4.5% of single-copy Drosophila DNA, corresponding to 6500 sequences of 1.4 kb. The LN of poly (A) tracts present in whole embryos, larvae, pupae, and imagos is in each case close to 70 nucleotides. RNA-driven reassociation experiments show that poly (A) + RNA from these sources contains, respectively, 3500, greater than or equal to 4900, 6900, and greater than or equal to 4900 sequences. Cross-hybridization reactions show extensive homology between these RNA populations. All five poly (A) + RNA preparations contain a prominent component with a sedimentation coefficient of 13 and a size of 1.78 kb, which is shown to be the larger species of mitochondrial rRNA. This rRNA binds to oligo (dT) cellulose and serves as an efficient template for cDNA synthesis by reverse transcriptase. In RNA-driven reassociation experiments it behaves like an abundant mRNA.