What is the ratio of spliced to unspliced introns in a cell? I found, that the median half-life of a human mRNA is roughly 10h [1], while transcription and splicing each take around half a minute [2, 3]. Based on this 1200x time-ratio, my default assumption is that the ratio between pre-mRNA and mRNA of the same genes follows a similar ratio.
Does this estimate seem reasonable? Are there any more direct experiments, that address this?
The context is crosslinking immunoprecipitation (CLIP), where some fragmented (and poly-(T) purified) RNA-reads might be only uniquely mapped if limiting mapping to the the pool of spliced mRNAs, while the same read may show up in introns. Knowing the ratio between introns and exons can help to evaluate the associated risk of such a simplification and to find suitable cut-offs.