Kinetic behavior of 30S rRNA intermediate labeled in developing embryonic cells of Xenopus laevis

In Xenopus neurula cells, "30S" RNA was found to be labeled with 3H-uridine after a relatively short labeling period. Results obtained from cumulative labeling and pulse-labeling and chase experiments with cells from late gastrulae, yolk plug-stage embryos, and neurulae showed that the 30S RNA is an intermediate in rRNA processing and is derived from 40S pre-rRNA and processed to 28S rRNA. The half-life of the 30S rRNA intermediate was about 7.5 min or less at the three stages examined.