The lognormal distribution fits the decay profile of eukaryotic mRNA

Abstract

A general program was written which simulates radioactive labeling of RNA in vivo . The program was used to determine the effect that different distributions of half-lives would have on the composite decay curve observed in a pulse-chase experiment. Four biologically relevant points emerge: 1) The published, experimentally determined composite decay curves for eukaryotic mRNA are not compatible with a normal, uniform, or exponential distribution of decay times. 2) The experimental curves are compatible with a lognormal distribution of decay times as well as the two-component discrete distribution previously hypothesized. 3) If the lognormal or some similar distribution were correct, about half the mRNA species would decay faster than what is presently called the “fast component of decay”. This point is crucial to any argument about the fraction of poly (A) or other nuclear sequence that is transported to the cytoplasm. 4) If a particular mRNA species is found to decay at a constant rate for 3 half-lives, that is not only consistent with 1 half-life for all the mRNA, but also consistent with 20 different half-lives which are normally or uniformly distributed. In addition to the decay of mRNA, the lognormal distribution is also compatible with data on the decay of poly(A)-containing nuclear RNA and total cellular protein.