Fragmentation and matching of human microRNA sequences in 3'utr.

AIMS Definition of sense and antisense microRNA matches in 3'utr. BACKGROUND Matches of mature microRNAs (m-miRs) in human 3'utr could be traced to mutations producing fragments of original m-miR sequences without physical separation. (The m-miR matches in 5'utr and cds should be by far fewer, but could follow similar patterns). OBJECTIVE To ascertain if the sense and antisense m-miR fragments in 3'utr occur at similar or different levels. METHODS Frequency of sense and antisense m-miR matches in 3'utr was examined in the range of 7-22 nucleotides. RESULTS The fragmentation occurs at gene level by mutation within one of the paired m-miRs, which upon transcription results in increased interactive capability for both former pre-micro (premir) RNA stem partners. The non-mutated stem partner can persist in 3'utr sequences, as is apparent from significant presence of miR-619-5p and miR-5096 and some conservation of 20 other simian- specific m-miR sequences. However, most of m-mir sequences in 3'utr are extensively fragmented, with low preservation of long matches. In flanks of individual m-miR embeds the mutated pre-mir positions are to a degree defined specifically. CONCLUSION The m-mir matches of various sizes in 3'utr apparently reflect accumulation, on a phylogenetic time scale, of in-sequence point mutations. Across human 3'utr this fragmentation is significantly less for evolutionarily recent human m-miRs that originate in simians compared to human m-miRs first appearing in lower primates, and especially to human m-miRs introduced in nonprimates.