RESUMO
Segment 7 of influenza B virus encodes two proteins, M1 and BM2. BM2 is expressed from a stop-start pentanucleotide, in which the BM2 initiation codon overlaps with the M1 stop codon. Here, we demonstrate that 45 nucleotides of the 3' end of the M1 coding region, but not the 5' end of the BM2 coding region, are sufficient for the efficient expression of the downstream protein. Placing these 45 nucleotides and the stop-start pentanucleotide in between the coding sequences induced the expression of at least three noninfluenza proteins, suggesting the utility of this system for expressing multiple proteins from one mRNA.
Assuntos
Vírus da Influenza B/metabolismo , Proteínas da Matriz Viral/metabolismo , Regulação da Expressão Gênica , Genes Reporter/genética , Vírus da Influenza B/genética , Mutação/genética , Nucleotídeos/genética , Nucleotídeos/metabolismo , Proteínas da Matriz Viral/genéticaRESUMO
This report describes the first isolation of the ameba Balamuthia mandrillaris from an environmental soil sample associated with a fatal case of amebic encephalitis in a northern California child. Isolation of the ameba into culture from autopsied brain tissue confirmed the presence of Balamuthia: In trying to locate a possible source of infection, soil and water samples from the child's home and play areas were examined for the presence of Balamuthia: The environmental samples (plated onto nonnutrient agar with Escherichia coli as a food source) contained, in addition to the ameba, a variety of soil organisms, including other amebas, ciliates, fungi, and nematodes, as contaminants. Presumptive Balamuthia amebas were recognized only after cultures had been kept for several weeks, after they had burrowed into the agar. These were transferred through a succession of nonnutrient agar plates to eliminate fungal and other contaminants. In subsequent transfers, axenic Naegleria amebas and, later, tissue cultures (monkey kidney cells) served as the food source. Finally, the amebas were transferred to cell-free axenic medium. In vitro, the Balamuthia isolate is a slow-growing organism with a generation time of approximately 30 h and produces populations of approximately 2 x 10(5) amebas per ml. It was confirmed as Balamuthia by indirect immunofluorescence staining with rabbit anti-Balamuthia serum and human anti-Balamuthia antibody-containing serum from the amebic encephalitis patient. The environmental isolate is similar in its antimicrobial sensitivities and identical in its 16S ribosomal DNA sequences to the Balamuthia isolate from the deceased patient.