. Data processing: insertion of exogenous mouse sequences
The GMO samples used in this research effort each contained an inserted transgene holding some exogenous, non-mouse, genomic sequences; specifically, the humanACTA1 gene region, the human TPM3 cDNA sequence, the four SV40 intronic regions, and the SB10 cassette ( Table 1, Fig. 1). Accordingly, high quality ChIP-seq reads that had failed to align to the mouse reference genome (i.e. unmapped reads) were aligned to a custom reference genomic library containing these exogenous genomic sequences (Fig. 2b). Sequence Alignment/Map tools (SAMtools 0.1.18; [16]) were used to generate FASTQ files for the unaligned reads, which were then aligned to the aforementioned reference library using the ELAND2 standalone aligner. Peak finding was executed on the resulting BAM files using MACS 1.4.2 to generate WIG files with the genome-size setting modified to represent the size of the reference used for alignment. The resulting peak data was then further examined and graphically represented MATLAB