Determining degradation intermediates and the pathway of 3' to 5' degradation of histone mRNA using high-throughput sequencing.

The half-life of an mRNA is an important parameter contributing to the steady-state level of the mRNA. Rapid changes in mRNA levels can result from decreasing the half-life of an mRNA. Establishing the detailed pathway of mRNA degradation for a particular class of mRNAs requires the ability to isolate mRNA degradation intermediates. High-throughput sequencing provides a method for detecting these intermediates. Here we describe a method for determining the intermediates in 3' to 5' degradation. Characterizing these intermediates requires not only determining the precise 3' end of the molecule to a single nucleotide resolution, but also the ability to detect and characterize any untemplated nucleotides present on the intermediates. We achieve this by ligating a known sequence to all the 3' termini in the cell, and then sequence the 3' termini and the ligated linker to identify any alterations to the genomic reference sequence. We have applied this method to characterize the intermediates in histone mRNA metabolism, allowing us to deduce the pathway of 3' to 5' degradation. This method can potentially be applied to any RNA, and we discuss possible strategies for extending the method to include simultaneous determination of the 3' and 5' end of the same RNA molecule.