Differential modes of chemical decay for early and late lambda messenger RNA

In the presence of rifampicin, chemical decay of pulse-labeled phage λ “early” messenger RNA occurred exponentially, with a half-life of 2.2 minutes at 42 °C, compared to 1.3 minutes for the host mRNA. In contrast, mRNA synthesized late during λ development exhibited a characteristic complex decay curve not previously observed for microbial mRNA; initial slow decay of about 25% during 4 to 4.5 minutes was followed by rapid exponential decay of the remainder with a half-life of 1.5 minutes. Sucrose density-gradient analyses of the RNA revealed that during the phase of slow decay, the λ-specific mRNA was progressively fragmented.