Researchers compared RNA sequences from human B cells of 27 individuals to the corresponding DNA sequences from the same individuals and uncovered more than 10,000 exonic sites where the RNA sequences do not match that of the DNA. These differences were nonrandom as many sites were found in multiple individuals and in different cell types, including primary skin cells and brain tissues. Using mass spectrometry, they detected peptides that are translated from the discordant RNA sequences and thus do not correspond exactly to the DNA sequences. They also compared the DNA and RNA sequences of the same individuals and found 28,766 events at over 10,000 exonic sites that differ between the RNA and the corresponding DNA sequence.
The underlying mechanisms for these events are largely unknown. For most of the cases, it is not known yet whether a different base was incorporated into the RNA during transcription or if these events occur posttranscriptionally. Anyway, these widespread RNA-DNA differences in the human transcriptome provide a yet unexplored aspect of genome variation.
Science. 2011 Jul 1;333(6038):53-8.