Genome-wide analysis revealed novel molecular features and evolution of Anti-codons in cyanobacterial tRNAs

Transfer RNAs (tRNAs) play important roles to decode the genetic information contained in mRNA in the process of translation. The tRNA molecules possess conserved nucleotides at specific position to regulate the unique function. However, several nucleotides at different position of the tRNA undergo modification to maintain proper stability and function. The major modifications include the presence of pseudouridine (Ψ) residue instead of uridine and the presence of m(5)-methylation sites. We found that, Ψ13 is conserved in D-stem, whereas Ψ38 & Ψ39 were conserved in the anti-codon loop (AL) and anti-codon arm (ACA), respectively. Furthermore, Ψ55 found to be conserved in the Ψ loop. Although, fourteen possible methylation sites can be found in the tRNA, cyanobacterial tRNAs were found to possess conserved G9, m(3)C(32), C(36), A(37), m(5)C(38) and U(54) methylation sites. The presence of multiple conserved methylation sites might be responsible for providing necessary stability to the tRNA. The evolutionary study revealed, tRNA(Met) and tRNA(Ile) were evolved earlier than other tRNA isotypes and their evolution is date back to at least 4000 million years ago. The presence of novel pseudouridination and m(5)-methylation sites in the cyanobacterial tRNAs are of particular interest for basic biology. Further experimental study can delineate their functional significance in protein translation.