Fig. 1
Steps in the TIPseq protocol. a Steps in TIPseq are shown from top to bottom in a vertical flow chart. These include (i.) vectorette adapter annealing, (ii.) genomic DNA (gDNA) digestion, (iii.) vectorette adapter ligation, (iv.) vectorette touchdown PCR, (v.) PCR amplicon shearing, (vi.) sequencing library preparation, (vii.) Illumina sequencing, and, (viii.) data analysis. The first seven of these steps are shown adjacent to schematic representations in part b., to the right. b Vectorette adapter annealing is shown first. Mismatched sequences within the hybridized vectorette oligonucleotides are illustrated in red and blue, and create a duplex structure with imperfect base pairing. The sticky end overhang on one strand of the vectorette (here, a 5ā² overhang on the bottom strand) is drawn in gray. This overhang in the annealed vectorette complements sticky ends left by genomic DNA digest, and the digest and vectorette ligations are shown in the subsequent two steps. The black box within the gDNA fragment illustrate a LINE-1 element of interest (i.e., a species-specific L1Hs). Most gDNA fragments will not have a transposable element of interest, and thus cannot be amplified efficiently by the vectorette PCR. In vectorette PCR, the L1Hs primer begins first strand synthesis (1) and extends this strand through the ligated vectorette sequence. The reverse primer complements this first-strand copy of the vectorette (2) and the two primers participate in exponential amplification (3) of these fragments in subsequent cycles. c Amplicons are sheared, and conventional Illumina sequencing library preparation steps complete the protocol. Paired-end sequencing reads are required to perform data analysis with TIPseqHunter. d A diagram of read pile-ups demonstrate how there is deep coverage of the 3ā² end of L1Hs elements. For elements on the plus (+) strand with respect to the reference genome, the amplified sequences are downstream of the insertion site (i.e., covering genomic coordinates ascending from the transposon insertion). For minus (ā) stranded insertions, sequences are recovered in the opposite direction