RESUMEN
We fused the epitope-recognizing fragment of heavy-chain antibodies from Camelidae sp. with fluorescent proteins to generate fluorescent, antigen-binding nanobodies (chromobodies) that can be expressed in living cells. We demonstrate that chromobodies can recognize and trace antigens in different subcellular compartments throughout S phase and mitosis. Chromobodies should enable new functional studies, as potentially any antigenic structure can be targeted and traced in living cells in this fashion.
Asunto(s)
Anticuerpos/química , Antígenos/química , Camelus/inmunología , Animales , Anticuerpos/inmunología , Reacciones Antígeno-Anticuerpo , Antígenos/inmunología , Epítopos , Proteínas Fluorescentes Verdes/química , Proteínas Fluorescentes Verdes/inmunología , Cadenas Pesadas de Inmunoglobulina/química , Cadenas Pesadas de Inmunoglobulina/inmunología , Mitosis , Fase SRESUMEN
To test the cellular response to an increased fatty acid oxidation, we generated a vector for an inducible expression of the rate-limiting enzyme carnitine palmitoyl-transferase 1alpha (CPT1alpha). Human embryonic 293T kidney cells were transiently transfected and expression of the CPT1alpha transgene in the tet-on vector was activated with doxycycline. Fatty acid oxidation was measured by determining the conversion of supplemented, synthetic cis-10-heptadecenoic acid (C17:1n-7) to C15:ln-7. CPT1alpha over-expression increased mitochondrial long-chain fatty acid oxidation about 6-fold. Addition of palmitic acid (PA) decreased viability of CPT1alpha over-expressing cells in a concentration-dependent manner. Both, PA and CPT1alpha over-expression increased cell death. Interestingly, PA reduced total cell number only in cells over-expressing CPT1alpha, suggesting an effect on cell proliferation that requires PA translocation across the mitochondrial inner membrane. This inducible expression system should be well suited to study the roles of CPT1 and fatty acid oxidation in lipotoxicity and metabolism in vivo.
Asunto(s)
Carnitina O-Palmitoiltransferasa/metabolismo , Ácidos Grasos/metabolismo , Riñón/citología , Riñón/metabolismo , Ácido Palmítico/metabolismo , Carnitina O-Palmitoiltransferasa/genética , Línea Celular , Supervivencia Celular/fisiología , Regulación de la Expresión Génica/fisiología , Humanos , Peroxidación de Lípido/fisiología , Oxidación-Reducción , Proteínas Recombinantes/metabolismoRESUMEN
The spatial and temporal organization of DNA replication was investigated in living cells with a green fluorescent protein fusion to the DNA polymerase clamp PCNA. In situ extractions and photobleaching experiments revealed that PCNA, unlike RPA34, shows little if any turnover at replication sites, suggesting that it remains associated with the replication machinery through multiple rounds of Okazaki fragment synthesis. Photobleaching analyses further showed that the transition from earlier to later replicons occurs by disassembly into a nucleoplasmic pool of rapidly diffusing subcomponents and reassembly at newly activated sites. The fact that these replication sites were de novo assembled in close proximity to earlier ones suggests that activation of neighboring origins may occur by a domino effect possibly involving local changes in chromatin structure and accessibility.