title: Extrachromosomal human immunodeficiency virus type 1 sequences are methylated in latently infected U937 cells.
abstract: Long-term human immunodeficiency virus type 1 (HIV-1) infection of the human monocytic cell line U937 resulted in a progressive loss of infectivity that was correlated with the accumulation of stable, extrachromosomal forms of viral DNA. Viral latency was also characterized by reduced levels of HIV-1 transcription. The structure and activity of extrachromosomal viral DNA (E-DNA) in a fully latent U937 cell line was investigated by molecular cloning and DNA transfection. The resulting 18-kb E-DNA clone was composed of an intact HIV-1 sequence flanked by 7 kb of host sequence to one side and 1 kb of host DNA to the other side. This configuration is the result of retroviral integration into a highly repetitive element of the Alu family. Transfection of the E-DNA clone resulted in the production of infectious virus, indicating that viral latency was not the result of mutations in the HIV-1 genome. Analysis of CCGG sites revealed extensive de novo methylation of viral sequences present within E-DNA. These results suggest that modification of extrachromosomal viral DNA sequences is a mechanism for HIV-1 latency in long-term infected U937 cells.
authors.affiliation: Aaron Diamond AIDS Research Center, New York, New York 10016.
authors.forename: M K
authors.initials: MK
authors.lastname: Singh
authors.forename: C D
authors.initials: CD
authors.lastname: Pauza
mesh_terms: D001483:Base Sequence; D003001:Cloning, Molecular; D004279:DNA, Viral / Q000235:genetics*; D005111:Extrachromosomal Inheritance; D015967:Gene Expression Regulation, Viral; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D066298:In Vitro Techniques; D008745:Methylation; D008969:Molecular Sequence Data; D009000:Monocytes / Q000382:microbiology*; D015183:Restriction Mapping; D014407:Tumor Cells, Cultured; D014779:Virus Replication
chemical_list: D004279:DNA, Viral