Cells contain many subcellular structures in which specialized proteins locally cluster. Binding interactions within such clusters may be analyzed in live cells using models for fluorescence recovery after photobleaching (FRAP). Here we analyze a three-dimensional FRAP model that accounts for a single spatially localized cluster of binding sites in the presence of both diffusion and impermeable...

Background Although the risk factors for breast cancer are well established, namely female gender, early menarche and late menopause plus the protective influence of early pregnancy, the underlying causes of breast cancer remain unknown. The development of substantial recent evidence indicates that a handful of viruses may have a role in breast cancer. These viruses are mouse mammary tumor viru...

A radioimmunoassay was developed that can detect and quantitate 3 ng or more of the avian RNA tumor virus reverse transcriptase. The assay detected no antigenic sites in Rous sarcoma virus alpha virions or in virions of a murine RNA tumor virus. About 70 molecules of reverse transcriptase were found per virion of avian myleloblastosis virus with this assay or with an assay based on antibody inh...

The in vitro transcription of the B-type mouse mammary tumor virus RNA into DNA is similar to that obtained with certain C-type viruses: synthesis can be initiated on an RNA primer molecule approximately the size of a tRNA, and a unique linkage (rA-dC) exists between this primer and the DNA product.

OBJECTIVE The mouse mammary tumor virus (MMTV) is the well-established etiological agent of mammary tumors in mice. A series of studies have implicated that a human murine mammary tumor virus-like virus occurs in human breast cancer, but it is unclear whether it has any causal role. METHODS The aim of the present study was to investigate the presence of MMTV env gene-like sequences in a group...

Transfer RNA methylases (rate and capacity) were studied in normal cells and tissues, in RNA and DNA oncogenic virus-transformed cells, and in tumors derived from the transformed cells. The DNA oncogenic virus-transformed cells (SV40 and polyoma) contained greater tRNA methylase capacities than their nontransformed normal cells. In contrast, no difference was observed (capacity or rate) between...

As part of a study of the cell surface changes associated with the production of murine mammary tumor virus, the structure of the envelope of this virus has been examined by using freeze-fracture techniques. Both fracture and deep-etch surfaces were examined. The fracture faces contain 10-nm spheres comparable to those observed on fractured plasma membranes, although fewer in number. Surfaces e...

Studies have highlighted the essential nature of a group of small, highly hydrophobic, membrane embedded, channel-forming proteins in the life cycles of a growing number of RNA viruses. These viroporins mediate the flow of ions and a range of solutes across cellular membranes and are necessary for manipulating a myriad of host processes. As such they contribute to all stages of the virus life c...

A procedure has been developed to map the genetic elements of avian tumor virus RNA, which has a molecular weight of about 3 X 10(6) daltons and a poly(A) sequence at the 3' end. For this purpose, about 30 RNase T1-resistant oligonucleotides were ordered relative to the 3'-poly(A) terminus of the RNA, to construct an oligonucleotide map of viral RNAs. A cluster of seven envelope gene (env)-spec...