Cloning of the left-end hairpin ( Figure S2B ). The DNA fragment SalI-BglII-nt93-518(BspEI)-576-XhoI-HindIII (containing the HBoV1 sequence nt 93-576), was amplified from the viral DNA and inserted into SaII/HindIII-digested pBBSmaI, to produce pBB2.1. Another DNA, SalI-nt1-86-BclI (containing HBoV1 nt 1-86 sequence), was synthesized according to the LEH sequence obtained in Figures 1A and 1B , and placed between the SalI and BglII sites in pBB2.1, with ligation of the BclI and BglII sites reproducing the HBoV1 sequence nt 87-92. The resultant plasmid harboring the 59 HBoV1 nt 1-576 sequence with an intact LEH is designated pBB-LEH.