Architecture of ribonucleoprotein complexes in influenza A virus particles

In viruses, as in eukaryotes, elaborate mechanisms have evolved to protect the genome and to ensure its timely replication and reliable transmission to progeny. Influenza A viruses are enveloped, spherical or filamentous structures, ranging from 80 to 120 nm in diameter. Inside each envelope is a viral genome consisting of eight single-stranded negative-sense RNA segments of 890 to 2,341 nucleotides each. These segments are associated with nucleoprotein and three polymerase subunits, designated PA, PB1 and PB2; the resultant ribonucleoprotein complexes (RNPs) resemble a twisted rod (10-15 nm in width and 30-120 nm in length) that is folded back and coiled on itself. Late in viral infection, newly synthesized RNPs are transported from the nucleus to the plasma membrane, where they are incorporated into progeny virions capable of infecting other cells. Here we show, by transmission electron microscopy of serially sectioned virions, that the RNPs of influenza A virus are organized in a distinct pattern (seven segments of different lengths surrounding a central segment). The individual RNPs are suspended from the interior of the viral envelope at the distal end of the budding virion and are oriented perpendicular to the budding tip. This finding argues against random incorporation of RNPs into virions, supporting instead a model in which each segment contains specific incorporation signals that enable the RNPs to be recruited and packaged as a complete set. A selective mechanism of RNP incorporation into virions and the unique organization of the eight RNP segments may be crucial to maintaining the integrity of the viral genome during repeated cycles of replication.     

米诺的尔对兔晶体上皮细胞增殖的影响

研究米诺的尔(Minoxidil)对体外培养的兔晶体上皮细胞增生的影响。将不同浓度的米诺的尔加入体外培养的兔晶体上皮细胞,分别作用24、48及72 h,采用MTT法观察米诺的尔对兔晶体上皮细胞增生的影响。将3.0 mmol的米诺的尔加入体外培养的兔晶体上皮细胞作用72 h,而后吸出药液,加入正常DMEM培养液继续培养96 h,观察米诺的尔在撤药96 h后对兔晶体上皮细胞增殖的抑制作用;并应用光学显微镜观察兔晶体上皮细胞在含或不含有3.0 mmol米诺地尔的培养液培养72h后的形态学变化。米诺的尔对兔晶体上皮细胞增生有抑制作用,呈浓度依赖性和时间依赖性。3.0 mmol米诺的尔对兔晶体上皮细胞增殖的抑制作用在撤除药液后并未降低,抑制作用持续增加。说明米诺的尔能有效抑制体外培养的兔晶体上皮细胞增生。     

Is ribonucleotide reductase the transforming function of herpes simplex virus 2?

Transformation of cells by herpes simplex virus 2 (HSV-2) can be induced by the BglII C (0.43-0.58 map units) or N (0.58-0.625) fragments of the viral genome. Sequences partially overlapping both fragments (0.566-0.602) encode two 3' coterminal mRNAs; these in turn direct the synthesis of two related polypeptides of molecular weight 140,000 (140K) and 35K (refs 4, 7), which may be involved in transformation. Recently, a temperature-sensitive (ts) mutation affecting HSV-induced ribonucleotide reductase has been mapped within this common region (B.M. Dutia, personal communication). We have partially purified the induced reductase and raised a rabbit antiserum to it which inhibits the enzyme activity and immunoprecipitates from infected cells a 144K polypeptide and minor species including a 38K polypeptide. Here we show that a monoclonal antibody to the putative transforming proteins competes with the rabbit serum for the 144K and 38K antigens and also immunoprecipitates specifically the induced reductase activity. These results suggest a possible role for ribonucleotide reductase in HSV-2-induced transformation.     

Orthotopic bone induction at sites of Moloney murine sarcoma virus inoculation in mice.

Moloney murine sarcoma virus (M-MSV) induces at the site of inoculation in newborn and adult mice and rats various types of sarcoma, including osteosarcoma. The induced tumours are fatal in newborn, whereas sarcomas developed in adult animals regress spontaneously. The regression is mediated mainly by a cellular response. We have now demonstrated that the presence of sarcomas induced by M-MSV is a powerful stimulus for periosteal osteogenesis around tumour masses. Orthotopically induced osteogenesis by M-MSV may serve as a model for local regulation of bone growth and for cell differentiation studies, and may help explain the aetiology of some human bone disorders.