RESUMO
Unwanted evolution of designed DNA sequences limits metabolic and genome engineering efforts. Engineered functions that are burdensome to host cells and slow their replication are rapidly inactivated by mutations, and unplanned mutations with unpredictable effects often accumulate alongside designed changes in large-scale genome editing projects. We developed a directed evolution strategy, Periodic Reselection for Evolutionarily Reliable Variants (PResERV), to discover mutations that prolong the function of a burdensome DNA sequence in an engineered organism. Here, we used PResERV to isolate Escherichia coli cells that replicate ColE1-type plasmids with higher fidelity. We found mutations in DNA polymerase I and in RNase E that reduce plasmid mutation rates by 6- to 30-fold. The PResERV method implicitly selects to maintain the growth rate of host cells, and high plasmid copy numbers and gene expression levels are maintained in some of the evolved E. coli strains, indicating that it is possible to improve the genetic stability of cellular chassis without encountering trade-offs in other desirable performance characteristics. Utilizing these new antimutator E. coli and applying PResERV to other organisms in the future promises to prevent evolutionary failures and unpredictability to provide a more stable genetic foundation for synthetic biology.
Assuntos
DNA Polimerase I/genética , DNA Bacteriano/genética , Evolução Molecular Direcionada/métodos , Endorribonucleases/genética , Proteínas de Escherichia coli/genética , Escherichia coli/genética , Plasmídeos/química , Sequência de Bases , Variações do Número de Cópias de DNA , DNA Polimerase I/metabolismo , Replicação do DNA , DNA Bacteriano/metabolismo , Endorribonucleases/metabolismo , Escherichia coli/metabolismo , Escherichia coli/efeitos da radiação , Proteínas de Escherichia coli/metabolismo , Engenharia Genética/métodos , Taxa de Mutação , Plasmídeos/metabolismo , Seleção Genética , Análise de Sequência de DNA , Biologia Sintética , Raios UltravioletaRESUMO
El cáncer de mama en hombres es una entidad poco frecuente y muy poco estudiada. Su pronóstico y manejo aun distan de lo ideal y de lo que se ha logrado en cáncer mamario en mujeres. Los tumores neuroendocrinos de la mama son aún más raros. Su comportamiento tiende en la mayoría de los casos a ser incierto y su manejo controversial. El reporte de caso se trata de un paciente masculino de 67 años, con historia de aparición de masa en mama derecha, con diagnóstico inicial de tumor mal diferenciado, con posterior inmunohistoquimica que informa tumor neuroendocrino primario de la mama. El diagnóstico temprano de cáncer de mama en hombres implica un verdadero reto para los sistemas de salud. Debemos conocer más sobre su fisiopatología y factores de riesgo(AU)
The early diagnosis of breast cancer in men represents a real challenge for the health systems. Therefore, our knowledge about its physiopathology and risk factors must be expandedBreast cancer in men is a rare and poorly studied malady. The prognosis and management is far from being ideal and from the achievements of the female breast cancer treatment. Even rare are neuroendocine breast tumors. In most of cases, its behavior is uncertain and its management is controversial. This was the report of a male patient aged 67 years, with history of right breast mass, initially diagnosed as a poorly differentiated tumor with later immunohistochemical test that reported the existence of a primary neuroendocrine breast tumor(AU)