A cis-Acting Element Present within the gag Open Reading Frame Negatively Impacts on the Activity of the HIV-1 IRES

Translation initiation from the human immunodeficiency virus type-1 (HIV-1) mRNA can occur through a cap or an IRES dependent mechanism. Cap-dependent translation initiation of the HIV-1 mRNA can be inhibited by the instability element (INS)-1, a cis-acting regulatory element present within the gag open reading frame (ORF). In this study we evaluated the impact of the INS-1 on HIV-1 IRES-mediated translation initiation. Using heterologous bicistronic mRNAs, we show that the INS-1 negatively impact on HIV-1 IRES-driven translation in in vitro and in cell-based experiments. Additionally, our results show that the inhibitory effect of the INS-1 is not general to all IRESes since it does not hinder translation driven by the HCV IRES. The inhibition by the INS-1 was partially rescued in cells by the overexpression of the viral Rev protein or hnRNPA1

Regulation of human papillomavirus gene expression by splicing and polyadenylation.

Human papillomaviruses (HPVs) are small DNA tumour viruses that are present in more than 99% of all cervical cancers. The ability of these viruses to cause disease is partly attributed to the strict coordination of viral gene expression with the differentiation stage of the infected cell. HPV gene expression is regulated temporally at the level of RNA splicing and polyadenylation, and a dysregulated gene expression programme allows some HPV types to establish long-term persistence, which is a risk factor for cancer. In this Review, we summarize the role of splicing and polyadenylation in the regulation of HPV gene expression and discuss the viral and cellular factors that control these processes