Degradation of cellular mRNA is a general early apoptosis-induced event

The fate of cellular mRNAs was analyzed in several cell lines of lymphoid origin, after induction of apoptosis by different mechanisms. Cytoplasmic mRNAs are specifically degraded as part of the early apoptotic response. This degradation is not species restricted and is independent of the cell line, the apoptotic stimulus, the intrinsic half-life of the mRNAs, and the transcriptional status of the gene (constitutive or inducible). mRNA degradation precedes DNA fragmentation and correlates with the appearance of phosphatidylserine in the outer cell membrane. In addition, apoptosis-induced mRNA degradation is an active process that can be dissected from other apoptotic hallmarks (degradation of annexin V, DNA, and poly(ADP-ribose) polymerase [PARP]), which suggests that apoptosis-induced mRNA degradation is controlled by a distinct signaling pathway. Furthermore, mRNA degradation also occurs in vivo, specifically during thymocyte apoptosis. Taken together, these data support the notion that degradation of mRNA is a general early apoptotic event that may become a new apoptotic hallmark.