RV integrations and transcription start sites. Distribution of gamma-RV (A) and LV (B) integration sites in human CD34⁺ cells within an interval of 30 kb upstream or downstream from the transcription start site (TSS) of known genes (UCSC definition, considering only 1 isoform/gene). The bars show the percentage of distribution in each 5-kb interval of retroviral insertions (□), insertion hot spots (■), and control sequences (▩). The line shows the distribution of 65 000 computer-generated random insertion sites.²⁶  n values indicate vector-gene interactions (ie, the total number of genes within 30 kb from individual insertions plus the intergenic insertions).