ИСТИНА

Intron sliding is a rare evolutionary event when intron shifts over short distances (1-15 bp). It might lead to a change of intron phase, i.e. the position of intron relative to the open reading frame, but it does not affect the total sequence of the transcript. Due to its ambiguous molecular mechanism and frequent errors in gene annotation, the existence of intron sliding could still be debatable. Here we look for sliding cases between humans and 13 different mammals including chimpanzees, rhesus macaques and mice. The thorough comparison of exon-intron boundaries in the pairwise genome alignments from UCSC Genome Browser showed that the sliding is indeed very rare - the maximum number of hits for each analyzed pair of organisms does not exceed 15. To confirm that the sliding events found represent a real phenomenon (and are not the result of gene annotation error) we used various transcriptome datasets of analyzed organisms from the NCBI SRA database as supporting evidence. Transcriptome analysis confirmed almost 80% of cases. However, the majority of these slided introns seemed to be in the low frequency isoforms. Another curious observation is that the sliding tends to happen in the last intron, in other words, at the end of gene. This might be due to the functional unimportance of that part of gene. To summarize, we were able to show well-confirmed intron sliding occurrences in mammal genomes and found new sliding-related features that should be studied in future work. The study was funded by RFBR according to the research project № 18-34-00932