RESUMO
Cross-linking experiments were performed with human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) mutants with unique cysteine residues at several positions (positions 65, 67, 70, and 74) in the fingers subdomain of the p66 subunit. Two approaches were used--photoaffinity cross-linking and disulfide chemical cross-linking (using an oligonucleotide that contained an N(2)-modified dG with a reactive thiol group). In the former case, cross-linking can occur to any nucleotide in either DNA strand, and in the latter case, a specific cross-link is produced between the template and the enzyme. Neither the introduction of the unique cysteine residues into the fingers nor the modification of these residues with photocross-linking reagents caused a significant decrease in the enzymatic activities of RT. We were able to use this model system to investigate interactions between specific points on the fingers domain of RT and double-stranded DNA (dsDNA). Photoaffinity cross-linking of the template to the modified RTs with Cys residues in positions 65, 67, 70, and 74 of the fingers domain of the p66 subunit was relatively efficient. Azide-modified Cys residues produced 10 to 25% cross-linking, whereas diazirine modified residues produced 5 to 8% cross-linking. Disulfide cross-linking yields were up to 90%. All of the modified RTs preferentially photocross-linked to the 5' extended template strand of the dsDNA template-primer substrate. The preferred sites of interactions were on the extended template, 5 to 7 bases beyond the polymerase active site. HIV-1 RT is quite flexible. There are conformational changes associated with substrate binding. Cross-linking was used to detect intramolecular movements associated with binding of the incoming deoxynucleoside triphosphate (dNTP). Binding an incoming dNTP at the polymerase active site decreases the efficiency of cross-linking, but causes only modest changes in the preferred positions of cross-linking. This suggests that the interactions between the fingers of p66 and the extended template involve the "open" configuration of the enzyme with the fingers away from the active site rather than the closed configuration with the fingers in direct contact with the incoming dNTP. This experimental approach can be used to measure distances between any site on the surface of the protein and an interacting molecule.
Assuntos
Transcriptase Reversa do HIV/genética , HIV-1/genética , Reagentes de Ligações Cruzadas , DNA/química , DNA/genética , Transcriptase Reversa do HIV/química , HIV-1/química , Humanos , Conformação de Ácido Nucleico , Especificidade por Substrato , Moldes GenéticosRESUMO
The healing of ischemic wounds is a particularly difficult clinical challenge. In this study, rabbit dermal fibroblasts transduced retrovirally with human platelet-derived growth factor B (PDGF-B) and human vascular endothelial growth factor 121 (VEGF121) genes were used to treat wounds in a rabbit ischemic ear model. The PDGF-B and VEGF121 genes were obtained from human umbilical vein endothelial cells (HUVECs) by reverse transcription-polymerase chain reaction, cloned into retroviral vectors under control of the beta-actin promoter, and introduced into primary rabbit dermal fibroblast cells. In vitro results demonstrated that rabbit dermal fibroblasts are transduced and selected readily using retroviral vectors, and are engineered to secrete PDGF-B and VEGF121 at steady-state levels of 150 ng per 10(6) cells per 24 hours and 230 ng per 10(6) cells per 24 hours respectively. These cells were then seeded onto polyglycolic acid (PGA) scaffold matrices and used to treat ischemic rabbit ear wounds. Immunohistochemistry showed intense staining for PDGF-B and VEGF121 in the wounds treated with these transduced cells compared with the control treatment groups. For the relatively more ischemic distal ear wounds, granulation tissue deposition was increased significantly in the wounds treated with PDGF-B- and VEGF121-transduced cells compared with wounds treated with PGA alone. These results demonstrate that gene augmentation of rabbit dermal fibroblasts with the PDGF-B and VEGF121 genes introduced into this ischemic wound model via PGA matrices modulates wound healing, and may have clinical potential in the treatment of ischemic wounds.
Assuntos
Fatores de Crescimento Endotelial/genética , Fibroblastos/citologia , Vetores Genéticos , Implantes Experimentais , Linfocinas/genética , Proteínas Proto-Oncogênicas c-sis/genética , Retroviridae , Pele/citologia , Transdução Genética , Cicatrização , Ferimentos e Lesões/terapia , Animais , Materiais Biocompatíveis , Engenharia Biomédica , Northern Blotting , Células Cultivadas , Orelha Externa/lesões , Orelha Externa/patologia , Fatores de Crescimento Endotelial/análise , Ensaio de Imunoadsorção Enzimática , Fibroblastos/metabolismo , Expressão Gênica , Humanos , Isquemia/complicações , Linfocinas/análise , Masculino , Ácido Poliglicólico , Proteínas Proto-Oncogênicas c-sis/análise , RNA/análise , Coelhos , Fator A de Crescimento do Endotélio Vascular , Fatores de Crescimento do Endotélio Vascular , Ferimentos e Lesões/patologia , Ferimentos e Lesões/fisiopatologiaRESUMO
N-Hydroxysuccinimide ester of 3-[3-(3-(trifluoromethyl)diazirin-3-yl)phenyl]-2,3-dihydroxypro pionic acid was successfully tested in a ribosomal tRNA binding system. It is an originally designed trifluoromethyl-diazirine-based cleavable cross-linking reagent with a very short distance between the active points (about 8.5 A). The reagent was coupled to the amino acid amino group of Phe-tRNAPhe to obtain a photoactivatable analog of peptidyl-tRNA. This analog was bound to ribosomes and the complex was irradiated with uv light. After isolation, the cross-linked product was cleft by periodate treatment to reveal the properties of the new reagent.