Table 1.

Retroviral integration site distributions.

Virus/vector	Percentage of integration sites		Description
	In genes*	In CpG islands‡
MLV§	43.3	17.7	§§ Strong preference for transcript start sites
HIV¶	65.2	1.5	¶¶ Strong preference for transcription units
ASLV#	42.9	2.7	Weak preference for transcription units
Foamy**	28.6	9.9	Modest preference for transcript start sites
Random‡‡	34.1	2.6	NA

^*Within the transcribed region of Refseq genes, human genome build 35 (hg17).

^‡In a CpG island or within 1 kilobase.

^§644 Murine leukemia virus (MLV) integrations in HeLa cells from [22], as analyzed in [25].

^¶1757 HIV integrations in primary lung fibroblasts (426), PBMCs (487), SupT1 cells (504), H9 cells (215) and HeLa (125) cells from [20,22,24], as analyzed in [25].

^#480 Avian sarcoma-leukosis virus (ASLV) integrations in HeLa (181) and 293T-TVA cells (299) from [23,24], as analyzed in [25].

^**2829 Foamy integrations in normal human fibroblasts (1008) and CD34⁺ hematopoietic cells (1,821) [25].

^‡‡10,000 randomly generated sites as previously described [25].

^§§Strong as defined by > 15% and modest as defined by between 10 and 12% of integrants within 2.5 kb of transcript start sites respectively.

^¶¶Strong as defined by > 60% and weak as defined by < 45% of integrants within transcription units respectively.

NA: Not applicable.