Cloning of the right-end hairpin ( Figure S2C ). The DNA fragment SalI-nt4097-4139(BglII)-5427(KasI)-ApaI (containing the HBoV1 nt 4097-5427 sequence) was amplified from viral DNA and inserted into SaII/ApaI-digested pBBSmaI, resulting in pBB2.2. Another DNA fragment, ApaI-nt5460(KasI)-5543-XhoI (containing HBoV1 nt 5460-5543 sequence) was synthesized based on the REH sequence ( Figure 1C ) and placed between the ApaI and HindIII sequences in pBB2.2, resulting in pBB-REH(D5428-5459). The missing short fragment between the two KasI sites encompassing nt 5428-5459 was recovered by a synthesized KasI linker based on the REH sequence ( Figure 1C ) and inserted into KasI-digested pBB-REH(D5428-5459). The resultant plasmid harboring the 39 HBoV1 nt 4097-5543 sequence with an intact REH is designated pBB-REH.