The human T-cell leukemia virus type 1 (HTLV-1) basic leucine zipper factor (HBZ) gene is encoded by the minus strand of the HTLV-1 provirus and transcribed from the 3 long terminal repeat (LTR). HBZ gene expression not only inhibits the Tax-mediated activation of viral gene transcription through the 5 LTR but also promotes the proliferation of infected cells. However, the HBZ promoter region and the transcriptional regulation of the gene have not been studied. In this study, we characterize the promoters of the spliced version of the HBZ gene (sHBZ) and the unspliced version of the HBZ gene (usHBZ) by luciferase assay. Both promoters were TATA-less and contained initiators and downstream promoter elements. Detailed studies of the promoter for the sHBZ gene showed that Sp1 sites were critical for its activity. The activities of the sHBZ and usHBZ gene promoters were upregulated by Tax through Taxresponsible elements in the 3 LTR. We compared the functions of the proteins derived from the sHBZ and usHBZ transcripts. sHBZ showed a stronger suppression of Tax-mediated transcriptional activation through the 5 LTR than did usHBZ; the level of suppression correlated with the level of protein produced. The expression of sHBZ had a growth-promoting function in a T-cell line, while usHBZ expression did not. This study demonstrates that Sp1 is critical for sHBZ transcription, which accounts for the constitutive expression of the sHBZ gene. Functional differences between sHBZ and usHBZ suggest that the sHBZ gene plays a significant role in the proliferation of infected cells.

Moving from a general revise of the structural and electronic properties of the 3D methylammoniumtrihalogenoplumbates (MAPbX3, X = Cl, Br, I) class of halide organic–inorganic perovskites, we have focused our attention on the organic cation and studied the role it plays in the electronic/optical features of this class of compounds, paying attention mainly to the iodide compound. We found good agreement with previous experimental works, but at the same time we observed that the bare inorganic network [PbX3]− does not fully take into account the electronic properties of 3D systems. A comparison is performed between the electronic properties of MAPbI3 organic–inorganic perovskite and those of the purely inorganic CsPbI3. Furthermore, we show that hybrid methods applied on top of the spin–orbit calculated structures are not able to open the bandgap sufficiently to reproduce the experimental value, revealing the need of further and more computationally demanding procedures to get improved agreement.

Three-dimensional organic-inorganic lead iodide perovskites are potential photoconductive materials for solar cells. Nowadays, a high power conversion efficiency exceeding 20% can be achieved. However, perovskite solar cells are reported to suffer from a large hysteresis in the current-voltage curves. This may be attributed to the motion of organic cations with a permanent dipole moment in response to the applied electric field. Therefore, in order to suppress the hysteresis, organic cations that have a zero dipole moment and a molecular size well fitted to the lead iodide cavity are required. Using density functional theory calculations, we theoretically studied the thermodynamic stability and electronic properties of lead iodide perovskites with large guanidinium cations having a nearly zero dipole moment, and compared the results with those predicted via the Goldschmidt tolerance factor. The properties of formamidiniumguanidinium (FA 1-x GA x PbI 3 ) intermediate alloys were also investigated.