Characterization of Circulating Transfer RNA-Derived RNA Fragments in Cattle

The objective was to to characterize naturally occurring circulating transfer RNA-derived RNA Fragments (tRFs) in cattle. Serum from eight adult dairy cows was collected, and RNA was extracting immediately after collection and sequenced in a high throughput system. Sequences aligned to transfer RNA (tRNA) genes or their flanking sequences were characterized. Sequences aligned to the beginning of 5’ end of the mature tRNA were classified as tRF-5; those aligned to the 3’ end of mature tRNA were classified as tRF-3; and those aligned to the beginning of the 3’ end flanking sequences were classified as tRF-1. There were 3,190,962 sequences that mapped to tRNA in the bovine genome. Of these, 2,323,520 were identified as tRF-5, 562 were tRF-3, and 81 were tRF-1. The tRF-5 ranged from 28 to 40 nucleotides; and 98.7% ranged from 30 to 34 nucleotides in length. Amino acids with the most number of tRF-5 were Histidine, Glutamic Acid, Lysine, Glycine, and Valine. There was no association between number of codons for each amino acid and number of tRFs in the samples. The reason why amino acids with the least number of codons have the most amount of tRF-5 can only be explained if these sequences are associated with function of the organism.