Regulation of cyclin T1 expression and function by an alternative splice variant that skips exon 7 and contains a premature termination codon.

Cyclin T1 (CCNT1), a gene containing nine exons, forms the positive transcription elongation factor b (P-TEFb) complex and regulates a wide variety of biological processes including transcription. We discovered a novel splice variant of CCNT1 that lacks exon 7 (dE7). RT-PCR analysis revealed that the dE7 transcript was detected in almost all tissues examined.

Derivatives of 5-nitro-furan-2-carboxylic acid carbamoylmethyl ester inhibit RNase H activity associated with HIV-1 reverse transcriptase.

The RNase H activity associated with human immunodeficiency virus type 1 (HIV-1) is an attractive target for an antiretroviral drug development. We screened 20000 small-molecular-weight compounds for RNase H inhibitors and identified a novel RNase H-inhibiting structure characterized by a 5-nitro-furan-2-carboxylic acid carbamoylmethyl ester (NACME) moiety. Two NACME derivatives, 5-nitro-furan-2-carboxylic acid adamantan-1-carbamoylmethyl ester (compound 1) and 5-nitro-furan-2-carboxylic acid [[4-(4-bromo-phenyl)-thiazol-2-yl]-(tetrahydro-furan-2-ylmethyl)-carbamoyl]-methyl ester (compound 2), effectively blocked HIV-1 and MLV RT-associated RNase H activities with IC(50)s of 3-30 microM but had little effect on bacterial RNase H activity in vitro.

Ligand-independent higher-order multimerization of CXCR4, a G-protein-coupled chemokine receptor involved in targeted metastasis.

CXCR4, a G-protein-coupled receptor of CXCL12/stromal cell-derived factor-1alpha, mediates a wide range of physiological and pathological processes, including the targeted metastasis of cancer cells. CXCR4 has been shown to homo-oligomerize in several experimental systems. However, it remains unclear with which domains CXCR4 interacts homotypically, and whether it dimerizes or forms a higher-order complex.

Substitution of the myristoylation signal of human immunodeficiency virus type 1 Pr55Gag with the phospholipase C-delta1 pleckstrin homology domain results in infectious pseudovirion production.

The matrix domain (MA) of human immunodeficiency virus type 1 Pr55Gag is covalently modified with a myristoyl group that mediates efficient viral production. However, the role of myristoylation, particularly in the viral entry process, remains uninvestigated. This study replaced the myristoylation signal of MA with a well-studied phosphatidylinositol 4,5-biphosphate-binding plasma membrane (PM) targeting motif, the phospholipase C-delta1 pleckstrin homology (PH) domain.

Identification of the P-TEFb complex-interacting domain of Brd4 as an inhibitor of HIV-1 replication by functional cDNA library screening in MT-4 cells.

We conducted a phenotypic cDNA screening using a T cell line-based assay to identify human genes that render cells resistant to human immunodeficiency virus type 1 (HIV-1). We isolated potential HIV-1 resistance genes, including the carboxy terminal domain (CTD) of bromodomain-containing protein 4 (Brd4). Expression of GFP-Brd4-CTD was tolerated in MT-4 and Jurkat cells in which HIV-1 replication was markedly inhibited.

Cyclin K/CPR4 inhibits primate lentiviral replication by inactivating Tat/positive transcription elongation factor b-dependent long terminal repeat transcription.

The positive transcription elongation factor b complexes comprise CDK9 and a C-type cyclin, required for the efficient expression of both eukaryotic and primate lentivirus-encoded genes. Cyclin K/CPR4 is the least studied of the positive transcription elongation factor b-forming cyclins. Here, we demonstrate that cyclin K/CPR4-containing positive transcription elongation factor b complexes are unresponsive to Tat and HEXIM1-mediated inactivation.

Inhibiting lentiviral replication by HEXIM1, a cellular negative regulator of the CDK9/cyclin T complex.

Objective: Tat-dependent transcriptional elongation is crucial for the replication of HIV-1 and depends on positive transcription elongation factor b complex (P-TEFb), composed of cyclin dependent kinase 9 (CDK9) and cyclin T. Hexamethylene bisacetamide-induced protein 1 (HEXIM1) inhibits P-TEFb in cooperation with 7SK RNA, but direct evidence that this inhibition limits the replication of HIV-1 has been lacking. In the present study we examined whether the expression of FLAG-tagged HEXIM1 (HEXIM1-f) affected lentiviral replication in human T cell lines.

Separate elements are required for ligand-dependent and -independent internalization of metastatic potentiator CXCR4.

The C-terminal cytoplasmic domain of the metastatic potentiator CXCR4 regulates its function and spatiotemporal expression. However, little is known about the mechanism underlying constitutive internalization of CXCR4 compared to internalization mediated by its ligand, stromal cell-derived factor-1 alpha (SDF-1alpha)/CXCL12. We established a system to analyze the role of the CXCR4 cytoplasmic tail in steady-state internalization using the NP2 cell line, which lacks endogenous CXCR4 and SDF-1alpha.

Rapid propagation of low-fitness drug-resistant mutants of human immunodeficiency virus type 1 by a streptococcal metabolite sparsomycin.

Here we report that sparsomycin, a streptococcal metabolite, enhances the replication of HIV-1 in multiple human T cell lines at a concentration of 400 nM. In addition to wild-type HIV-1, sparsomycin also accelerated the replication of low-fitness, drug-resistant mutants carrying either D30N or L90M within HIV-1 protease, which are frequently found mutations in HIV-1-infected patients on highly active antiretroviral therapy (HAART). Of particular interest was that replication enhancement appeared profound when HIV-1 such as the L90M-carrying mutant displayed relatively slower replication kinetics.

The interaction of HIV-1 with the host factors.

Human immunodeficiency virus type 1 (HIV-1) is a causative agent of acquired immunodeficiency syndrome (AIDS) in humans. In the last decade, the functions of HIV-1-encoded genes have been intensively studied. These studies have contributed to the development of the effective anti-AIDS drugs directing against the HIV-1-encoded enzymes, namely reverse transcriptase and protease.