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Activity of the human immunodeficiency virus type 1 cell cycle-dependent internal ribosomal entry site is modulated by IRES trans-acting factors

Vallejos, Maricarmen, Deforges, Jules, Plank, Terra-Dawn M., Letelier, Alejandro, Ramdohr, Pablo, Abraham, Christopher G., Valiente-Echeverría, Fernando, Kieft, Jeffrey S., Sargueil, Bruno, López-Lastra, Marcelo
Nucleic acids research 2011 v.39 no.14 pp. 6186-6200
Human immunodeficiency virus 1, RNA, cell cycle, models, mutation, ribosomes, transactivators, translation (genetics)
The 5' leader of the human immunodeficiency virus type 1 (HIV-1) genomic RNA harbors an internal ribosome entry site (IRES) that is functional during the G2/M phase of the cell cycle. Here we show that translation initiation mediated by the HIV-1 IRES requires the participation of trans-acting cellular factors other than the canonical translational machinery. We used 'standard' chemical and enzymatic probes and an 'RNA SHAPE' analysis to model the structure of the HIV-1 5' leader and we show, by means of a footprinting assay, that G2/M extracts provide protections to regions previously identified as crucial for HIV-1 IRES activity. We also assessed the impact of mutations on IRES function. Strikingly, mutations did not significantly affect IRES activity suggesting that the requirement for pre-formed stable secondary or tertiary structure within the HIV-1 IRES may not be as strict as has been described for other viral IRESes. Finally, we used a proteomic approach to identify cellular proteins within the G2/M extracts that interact with the HIV-1 5' leader. Together, data show that HIV-1 IRES-mediated translation initiation is modulated by cellular proteins.