Figure 2.

Genomic integration mechanism of tRNA-derived tailless retropseudogenes. (A) RNA break point (arrow) and priming site (boxed nucleotides) in an example in which a fragment of pre-tRNA^Cys serves as a tailless retropseudogene template. Tailless retropseudogene-specific substitutions differing from the presumed tRNA precursor template are encircled. Nucleotides representing the remainder of the tRNA precursor, but not part of the tailless retropseudogenes, are depicted as “thin” letters. (B) The genomic integration site with the consensus sequence TT/WX_1-17 (in this particular case, TT/WX₆) is shown above the bracket. The RNA priming site is boxed, the direction of reverse transcription is indicated by an arrow. The presumed single-stranded, staggered end is shown by a double-headed arrow, part of which (seven nucleotides in this case) acts as a DNA primer for reverse transcription. (C) Sequence of chromosomal locus after integration of the tailless retropseudogenes. Direct repeats (DR) are indicated by arrows. Note that the priming site (within the boxed tailless retropseudogenes) is part of the DR.