Fig. 7

Transcribed histone H3 coding sequence was captured by an hAT DNA transposon. a The intron-exon structure of the original histone H3 gene shows three exons (orange rectangles) connected by two lines representing the introns. b The histone H3 coding sequence showing the exon-exon boundaries, vertical black lines on the salmon-pink bar. The numbers at the exon-exon junction correspond to the amino acids at the beginning of exon2, exon3 and the last amino acid on exon3. Presence of exon-exon boundaries was used as an indication of transcribed coding sequence captured by the hAT DNA transposable elements. c Initially, tBLASTn identified the histone H3 copies in the hAT DNA transposon. d The initial search was refined by using histone hmm profiles with HMMER. The original sequences had very poor H3 domain hits due to numerous changes caused by repeat-induced point mutation (RIP). e The identification of H3-like sequence in deRIPped elements was substantially better. f However, the best result, i.e., all exon-exon boundaries were evident, was obtained when the deRIPped sequences were curated manually by removing the remaining stop codons that resulted from RIP. These protein alignments have been drawn to scale. The two horizontal bars in each panel represent the results from the two histone H3-like domains in the hAT element