Figure 4.

Distribution of L1 3' ends and L1 sequence A content. The histogram shows the annotated 3' endpoints of 332,587 young L1s that were collected from the human genome using RepeatMasker; the L1.3 sequence (GenBank accession number L19088.1) was used as the query library [11]. The L1 sequence was separated into bins of 50 nucleotides and each 3' end was placed into the appropriate bin. The line graph shows the proportion of A nucleotides in each 50-nucleotide bin of the L1.3 element. Below the graph is a schematic of the L1.3 element, and the red regions indicate locations that are at least 5 nucleotides long and with 85% or more A content. The arrows indicate the four A(7) regions.