Previously, we and others have demonstrated that the process of reverse transcription of human immunodeficiency virus type 1 (HIV-1) is disturbed in nondividing macrophages and quiescent T lymphocytes. Here we analyzed which phase of the cell cycle in macrophages is crucial for early steps in the HIV-1 replication cycle. HIV-1 Ba-L-inoculated macrophages arrested early in the G 1 phase by n-butyrate contained incomplete products of reverse transcription. In gamma-irradiated macrophages, reverse transcription was successfully completed but proviral integration could not be detected. In these cells, nuclear import was disturbed as reflected by the absence of two-long-terminal-repeat circles. In macrophages arrested late in G 1 phase by aphidicolin or 5,6-dichloro-1--D-ribofuranosyl-benzimidazole (DRB), reverse transcription was unaffected. Proviral integration occurred efficiently in DRB-treated macrophages, whereas integrated proviral DNA could not be detected after aphidicolin treatment. Arrest at G 2 phase of the cell cycle by nocodazole did not affect reverse transcription or proviral integration. Treatment of macrophages with hydroxyurea (HU), which reduces the intracellular deoxynucleoside triphosphate (dNTP) pool by blocking the de novo synthesis of dNTP, resulted in a dose-dependent inhibition of HIV-1 reverse transcription. This could partially be restored by the addition of nucleoside precursors. Addition of nucleoside precursors enhanced both reverse transcription and cell proliferation. However, the disturbed reverse transcription observed in the nonproliferating and n-butyrate-treated macrophages could not be restored by addition of nucleoside precursors. Similar to observations in quiescent T lymphocytes, incomplete proviral DNA species were arrested in the cytoplasm of the macrophages. Our results indicate that also in primary macrophages the intracellular nucleotide pools and other cellular factors that coincide with late G 1 phase of the cell cycle may contribute to efficient reverse transcription and nuclear localization.Oncoretroviruses depend on cycling cells for their replication. Passage through G 1 /S phase of the cell cycle is essential for efficient reverse transcription (6,16,26,28,29,46). The same has been demonstrated for human immunodeficiency virus type 1 (HIV-1). In nondividing cells the process of reverse transcription is disturbed, resulting in incomplete proviral DNA species both in quiescent T cells (50, 51) and in nondividing primary macrophages (32,33,43). Early events in cellular activation and cell proliferation have been demonstrated to regulate reverse transcription (31,34,43).For oncoretroviruses, it has also been demonstrated that nuclear transport of the large preintegration complex occurs only during mitosis, when the nuclear membrane is permeabilized (28,35,41,46). In that respect, HIV-1 was described to be different. HIV-1 nuclear transport did not require nuclear membrane permeabilization as seen during mitosis, and its replication was therefore considered to be cel...
