Post-transcriptional control of messenger RNA diversity in frog embryos.

The control of mRNA diversity during frog development has been investigated. Nuclear and messenger RNA from the early neurula and larval stages of Rana pipiens were hybridized in vast excess to labeled single-copy DNA and resistance to S1 nuclease was measured. Mixtures of RNA populations were also hybridized with single-copy DNA as a measurement of sequence overlap. Neurula and larval nuclear RNA hybridize to 11.3% and 12.1% of the single copy DNA. A mixture of both nuclear RNA populations hybridizes to 10.8% of the DNA, indicating a great amount of sequence overlap between the two populations. The mRNA complexity almost doubles during this developmental period from 4.7% of the single-copy DNA complexity at the early neurula to 8.7% at the larval stage. Mixtures of nuclear and messenger RNA were used to hybridize single-copy DNA and the results indicate that mRNA sequences present on neurula polysomes, but not on larval polysomes, are found in larval nuclei. Furthermore, mRNA sequences found on larval polysomes, but not on neurula polysomes, are found in the neurula nuclei. The data indicate that post-transcriptional events appear to play a role in the qualitative control of mRNA diversity during development.