Virology Commons^™

Purification And Characterization Of Two Forms Of A High-Molecular-Weight Cysteine Proteinase (Porphypain) From Porphyromonas Gingivalis, Pawel Ciborowski, Makoto Nishikata, Roger D. Allen, Marilyn S. Lantz

Nebraska Center for Virology: Faculty Publications

Porphyromonas gingivalis, an organism implicated in the etiology and pathogenesis of human periodontal diseases, produces a variety of potent proteolytic enzymes, and it has been suggested that these enzymes play a direct role in the destruction of periodontal tissues. We now report that two cell-associated cysteine proteinases of P. gingivalis W12, with molecular masses of approximately 150 kDa (porphypain-1) and 120 kDa (porphypain-2), as determined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, have been separated and purified to apparent homogeneity. These proteinases appear to be SDS-stable conformational variants of a 180-kDa enzyme, and they are the largest cysteine proteinases …

High Rates Of Frameshift Mutations Within Homo-Oligomeric Runs During A Single Cycle Of Retroviral Replication, Dawn P. Wooley, H. M. Temin

Neuroscience, Cell Biology & Physiology Faculty Publications

Homo-oligomeric runs were inserted into a spleen necrosis virus-based retrovirus vector to determine the nature and rate of mutations within runs of 10 to 12 identical nucleotides during a single replication cycle. Clones of helper cells containing integrated copies of retroviral vectors were used to produce virus for infection of target (nonhelper) cells. Proviral sequences from target cell clones were compared with proviral sequences from helper cell clones to study mutations that occurred during a single cycle of replication. In addition to the internal region spanning the homo-oligomeric inserts, a naturally occurring run of 10 T's in the long terminal …

Adoptive Transfer Of Polyclonal And Cloned Cytolytic T Lymphocytes (Ctl) Specific For Mouse Aids-Associated Tumors Is Effective In Preserving Ctl Responses: A Measure Of Protection Against Lp-Bm5 Retrovirus-Induced Immunodeficiency., William R. Green, Kathy A. Green, Karen M. Crassi

Dartmouth Scholarship

Cytolytic T lymphocytes (CTL) can be raised against C57BL/6 B-cell lymphomas from mice with LP-BM5 murine leukemia virus-induced AIDS (MAIDS). Adoptive transfer of polyclonal anti-MAIDS tumor CTL or two CTL clones specific for the B6-1710 MAIDS lymphoma caused preservation of major histocompatibility complex-restricted and allogeneic CTL responses, which may be interpreted as indices of protection from LP-BM5 murine leukemia virus-induced immunodeficiency.

Molecular Analysis Of The Rfb Gene Cluster Of A Group D2 Salmonella Enterica Strain: Evidence For Its Origin From An Insertion Sequence-Mediated Recombination Event Between Group E And Dl Strains, Shi-Hua Xiang, Matthew Hobbs, Peter R. Reeves

Nebraska Center for Virology: Faculty Publications

The Salmonella enterica O antigen is a highly variable surface polysaccharide composed of a repeated oligosaccharide (the O unit). The O unit produced by serogroup D2 has structural features in common with those of groups Dl and El, and hybridization studies had previously suggested that the D2 rfb gene cluster responsible for O-unit biosynthesis is indeed a hybrid of the two. In this study, the rfb gene cluster was cloned from a group D2 strain of S. enterica sv. Strasbourg. Mapping, hybridization, and DNA sequencing showed that the organization of the D2 rfb genes is similar to that of group …

Phylogenetic Associations Of Human And Simian T-Cell Leukemia/Lymphotropic Virus Type I Strains: Evidence For Interspecies Transmission, Igor J. Koralnik, Enzo Boeri, W. Carl Saxinger, Anita Lo Monico, Jake Fullen, Antoine Gessain, Hong-Guang Guo, Robert C. Gallo, Phillip Markham, Vaniambadi Kalyanaraman, Vanessa Hirsch, Jonathan Allan, Krishna Murthy, Patricia Alford, Jill Pecon-Slattery, Stephen J. O'Brien, Genoveffa Ranchini

Biology Faculty Articles

Homologous env sequences from 17 human T-leukemia/lymphotropic virus type I (HTLV-I) strains from throughout the world and from 25 simian T-leukemia/lymphotropic virus type I (STLV-I) strains from 12 simian species in Asia and Africa were analyzed in a phylogenetic context as an approach to resolving the natural history of these related retroviruses. STLV-I exhibited greater overall sequence variation between strains (1 to 18% compared with 0 to 9% for HTLV-I), supporting the simian origin of the modern viruses in all species. Three HTLV-I phylogenetic clusters or clades (cosmopolitan, Zaire, and Melanesia) were resolved with phenetic, parsimony, and likelihood analytical procedures. …

Phylogenetic Analysis Of Segment 10 From African Horsesickness Virus And Cognate Genes From Other Orbiviruses, Rafael O. De Sá, Marla Zellner, Marvin J. Grubman

Biology Faculty Publications

Utilizing the reverse transcriptase-polymerase chain reaction (RT-PCR) procedure, we have synthesized full-length copies of segment 10 from African horsesickness virus (AHSV) serotypes 1,4 and 8. The genes were cloned, sequenced and compared with the sequence of the cognate gene from AHSV serotypes 3 and 9. Sequences were analyzed to assess evolutionary relationships among serotypes using cladistics. Based on this analysis the data support a close relationship between serotypes 4 and 9 and between serotypes 1 and 8 and a closer relationship of serotype 3 to the 4 and 9 group.

The Amino-Terminal Functions Of The Simian Virus 40 Large T Antigen Are Required To Overcome Wild-Type P53-Mediated Growth Arrest Of Cells., Robin S. Quartin, Charles N. Cole, James M. Pipas, Arnold J. Levine

Dartmouth Scholarship

High levels of the p53 tumor suppressor protein can block progression through the cell cycle. A model system for the study of the mechanism of action of wild-type p53 is a cell line (T64-7B) derived from rat embryo fibroblasts transformed by activated ras and a temperature-sensitive murine p53 gene. At 37 to 39 degrees C, the murine p53 protein is in a mutant conformation and the cells actively divide, whereas at 32 degrees C, the protein has a wild-type conformation and the cells arrest in the G1 phase of the cell cycle. Wild-type simian virus 40 large T antigen and …

Virus Diseases Of Subterranean Clover Pastures And Their Management, David Ferris, Roger Jones

Journal of the Department of Agriculture, Western Australia, Series 4

In Western Australia and southern Australia generally, subterranean clover mottle (SCMV) and bean yellow mosaic (BYMV) are the most damaging virus diseases of subterranean clover pastures.

Although infected plants cannot be cured of virus infection, pastures can be managed to reduce both virus spread and persistence from year to year. Management options depend on which virus is present and include reseeding with resistant varieties; changing the pasture composition so that non-host species predominate; altering grazing practices to limit spread; and application of pesticide sprays to kill aphids.

Nonhomologous Rna Recombination In Tombusviruses: Generation And Evolution Of Defective Interfering Rnas By Stepwise Deletions, K. Andrew White, Thomas Jack Morris

Nebraska Center for Virology: Faculty Publications

We used a protoplast system to study the mechanisms involved in the generation and evolution of defective interfering (DI) RNAs of tomato bushy stunt tombusvirus (TBSV). Synthetic transcripts corresponding to different naturally occurring TBSV DI RNAs, or to various artificially constructed TBSV defective RNAs, were analyzed. The relative levels of competitiveness of different DI RNAs were determined by coinoculating their corresponding transcripts into protoplasts along with helper genomic RNA transcripts and monitoring the level of DI RNA accumulation. Further studies were performed to assess the contribution of naked DI RNA stability and DI RNA encapsidation efficiency to the observed levels …

Efficient Transcriptional Activation Of Many Simple Modular Promoters By Simian Virus 40 Large T Antigen., Philip W. Rice, Charles N. Cole

Dartmouth Scholarship

Simian virus 40 (SV40) large T antigen is a multifunctional protein which plays central roles during both lytic and transforming infections by SV40. It is a potent transcriptional activator and increases expression from the SV40 late promoter and from several cellular promoters. To understand better the transcriptional activation activity of large T antigen, we examined its ability to transactivate a set of simple modular promoters containing one of four upstream activation sequences coupled with one of three different TATA box sequences originally constructed and studied by Taylor and Kingston (Mol. Cell. Biol. 10:165-175, 1990). Large T antigen activated transcription from …

Infection Of Macrophages With Lymphotropic Human Immunodeficiency Virus Type 1 Can Be Arrested After Viral Dna Synthesis, Zheng-Bo Huang, Mary Jane Potash, Malgorzata Simm, Wei Chao, Howard Gendelman, Edward Edin, David J. Volsky

Nebraska Center for Virology: Faculty Publications

Lymphotropic strains of human immunodeficiency virus type 1 (HIV-1), including HTLV-IIIB, replicate poorly in macrophages. We have shown previously that lymphotropic HIV-1 fuses equally well with T lymphocytes and macrophages (M. J. Potash, M. Zeira, Z.-B. Huang, T. Pearce, E. Eden, H. Gendelman, and D. J. Volsky, Virology 188:864-868, 1992), suggesting that events in the virus life cycle following virus-cell fusion limit virus replication. We report here that HIV-1 DNA is synthesized effliciently in either ADA or HTLV-IIIB infected alveolar macrophages or monocyte-derived macrophages within 24 h of virus infection, as observed by polymerase chain reaction for amplification of viral …

Molecular Cloning Of Infectious Ecotropic Murine Leukemia Virus Ak7 From An Emv-14-Positive Akxl-5 Mouse And The Resistance Of Ak7 To Recognition By Cytotoxic T Lymphocytes., Hillary D. White, William R. Green, Nuria R. Giné

Dartmouth Scholarship

The AKXL-5 recombinant inbred mouse strain is positive for the endogenous ecotropic murine leukemia virus emv-14, the only emv present in its germ line. emv-14 is of particular interest because spleen cells expressing emv-14 virus escape recognition by anti-AKR/Gross virus-specific cytotoxic T lymphocytes. We report here the isolation and characterization of a replication-competent emv clone, pAK7, derived from an AKXL-5 mouse. This clone is novel in that it encodes a variant ecotropic murine leukemia virus that, when expressed in SC.Kb target cells, fails to be recognized efficiently by anti-AKR/Gross virus cytotoxic T lymphocytes. The pAK7 clone can therefore be used …

Isolation And Characterization Of New Wild-Type Isolates Of Bovine Lentivirus, David Suarez, Martin Van Der Maaten, Charles Wood, Ceclia Whetstone

Nebraska Center for Virology: Faculty Publications

Two new isolates of bovine lentivirus, also known as bovine immunodeficiency-like virus (BIV), were obtained from a seropositive cattle herd in Florida. This is the first report of new isolates of BIV since the original BIV strain, R29, was isolated in 1%9. The two new BIV isolates were derived from blood butFy coat cells cocultivated in vitro with fetal bovine lung cell cultures. The new isolates differed in vitro from the original R29 isolate in replication and syncytium formation in fetal bovine lung cells. Both new isolates were confirmed as BIV by immunofluorescence assay, Western blotting (immunoblotting), and polymerase chain …

Simian Immunodeficiency Virus Mutants Resistant To Serum Neutralization Arise During Persistent Infection Of Rhesus Monkeys, Dawn P. Wooley, Catherine Collignon, Ronald C. Desrosiers

Neuroscience, Cell Biology & Physiology Faculty Publications

We previously described the pattern of sequence variation in gp120 following persistent infection of rhesus monkeys with the pathogenic simian immunodeficiency virus SIVmac239 molecular clone (D.P.W. Burns and R.C. Desrosiers, J. Virol. 65:1843, 1991). Sequence changes were confined largely to five variable regions (V1 to V5), four of which correspond to human immunodeficiency virus type 1 (HIV-1) gp120 variable regions. Remarkably, 182 of 186 nucleotide substitutions that were documented in these variable regions resulted in amino acid changes. This is an extremely nonrandom pattern, which suggests selective pressure driving amino acid changes in discrete variable domains. In the present study, …

Identifying Bovine Respiratory Syncytial Virus By Reverse Transcription-Polymerase Chain Reaction And Oligonucleotide Hybridizations, R. D. Oberst, M. P. Hays, K. J. Hennessey, L. C. Stine, J. F. Evermann, Clayton L. Kelling

Nebraska Center for Virology: Faculty Publications

An assay to identify tissue culture cells infected with bovine respiratory syncytial virus (BRSV) that utilizes reverse transcription (RT), the polymerase chain reaction (PCR), and a synthetic oligonucleotide hybridization probe has been developed. The RT-PCR assay uses a BRSV-specific negative-sense oligonucleotide primer to synthesize cDNA from a BRSV fusion protein mRNA template and another BRSV-specific oligonucleotide primer (positive sense) upstream from the negative-sense primer for PCR amplification. In the presence of mRNA templates of BRSV isolates originating from locations throughout the United States, the BRSV RT-PCR assay resulted in amplified products (381 bp) that were specific to BRSV, as demonstrated …

Two Factors That Bind To Highly Conserved Sequences In Mammalian Type C Retroviral Enhancers., Nancy R. Manley, Mary M. O'Connell, Wanwen Sun, Nancy A. Speck, Nancy Hopkins

Dartmouth Scholarship

The transcriptional enhancers of the Moloney and Friend murine leukemia viruses (MLV) are important determinants of viral pathogenicity. We used electrophoretic mobility shift and methylation interference assays to study nuclear factors which bind to a region of these enhancers whose sequence is identical between Moloney and Friend viruses and particularly highly conserved among 35 mammalian type C retroviruses whose enhancer sequences have been aligned (E. Golemis, N. A. Speck, and N. Hopkins, J. Virol. 64:534-542, 1990). Previous studies identified sites for the leukemia virus factor b (LVb) and core proteins in this region (N. A. Speck and D. Baltimore, Mol. …

Characterization Of A Protein That Binds Multiple Sequences In Mammalian Type C Retrovirus Enhancers., Wanwen Sun, Mary M. O'Connell, Nancy A. Speck

Dartmouth Scholarship

Mammalian type C retrovirus enhancer factor 1 (MCREF-1) is a nuclear protein that binds several directly repeated sequences (CNGGN6CNGG) in the Moloney and Friend murine leukemia virus (MLV) enhancers (N. R. Manley, M. O'Connell, W. Sun, N. A. Speck, and N. Hopkins, J. Virol. 67:1967-1975, 1993). In this paper, we describe the partial purification of MCREF-1 from calf thymus nuclei and further characterize the binding properties of MCREF-1. MCREF-1 binds four sites in the Moloney MLV enhancer and three sites in the Friend MLV enhancer. Ethylation interference analysis suggests that the MCREF-1 binding site spans two adjacent minor grooves of …

Book Review: The Baculovirus Expression System: A Laboratory Guide (1992) King, L. A. & Possee, R. D., David D. Dunigan

Nebraska Center for Virology: Faculty Publications

The power of molecular biology is unleashed with the ability to clone and sequence genes, and then express these genes in heterologous systems. This sets the stage for the full analysis of proteins that are otherwise difficult to isolate and/or purify, especially when present at very low copy number per cell or when isolated from relatively precious materials. Overexpression of protein is now possible in a number of systems including prokaryotes (e.g., E. coli) and various eukaryotes (yeast, insects, and plants). The issue then becomes, which system (1) most closely reflects the homologous expression with respect to posttranslational modifications, …

Loss Of Infectivity By Progeny Virus From Alpha Interferon- Treated Human Immunodeficiency Virus Type 1-Infected T Cells Is Associated With Defective Assembly Of Envelope Gp120, Brian D. Hanson, Peter L. Nara, Radha K. Maheshwari, Girmel S. Sidhu, John G. Bernbaum, David Hoekzema, Monte S. Meltzer, Howard Gendelman

Nebraska Center for Virology: Faculty Publications

Levels of human immunodeficiency virus (HIV) DNA, RNA, or p24 antigen and reverse transcriptase activity in T-cell cultures treated with 500 IU of recombinant alpha interferon (rIFNα) per ml were comparable to those in control cultures. Radioimmunoprecipitation analysis of proteins in lysates of IFN-treated T cells documented a marked accumulation of HlV proteins. Localization of gp120 by immunofluorescence showed a diffuse pattern in IFN-treated cells quite distinct from the ring pattern in untreated control cells. That large quantities of a120 in aberrant cell compartments might affect HlV morphogenesis was confirmed in infectivity studies: virions from IFN-treated cells were 100- to …

Processing And Localization Of Dengue Virus Type 2 Polyprotein Precursor Ns3-Ns4a-Ns4b-Ns5, Luwen Zhang, P. Maruthi Mohan, R. Padmanabhan

Nebraska Center for Virology: Faculty Publications

Processing of dengue virus type 2 polyprotein precursor NS3-NS4A-NS4B-NS5 could be mediated by the catalytically active NS3 protease domain and NS2B in trans at the dibasic sites NS3-NS4A and NS4B-NS5. Subcellular localization of the unprocessed precursor NS3-NS4A-NS4B-NS5 showed that it was confined to a distinct subcellular organelle in the cytoplasm, which was distinct from the distribution of the mature NS5.

Worldwide Prevalence Of Lentivirus Infection In Wild Feline Species: Epidemiologic And Phylogenetic Aspects, Robert A. Olmstead, Raymond Langley, Melody E. Roelke, Robert M. Goeken, Diane Adger-Johnson, Julie P. Goff, John P. Albert, Craig Packer, M. Karen Laurenson, Tim M. Caro, Lue Scheepers, David E. Wildt, Mitchell Bush, Janice S. Martenson, Stephen J. O'Brien

Biology Faculty Articles

The natural occurrence of lentiviruses closely related to feline immunodeficiency virus (FIV) in nondomestic felid species is shown here to be worldwide. Cross-reactive antibodies to FIV were common in several free-ranging populations of large cats, including East African lions and cheetahs of the Serengeti ecosystem and in puma (also called cougar or mountain lion) populations throughout North America. Infectious puma lentivirus (PLV) was isolated from several Florida panthers, a severely endangered relict puma subspecies inhabiting the Big Cypress Swamp and Everglades ecosystems in southern Florida. Phylogenetic analysis of PLV genomic sequences from disparate geographic isolates revealed appreciable divergence from domestic …

Identification And Characterization Of The Bovine Immunodeficiency-Like Virus Tat Gene, Zhen-Qian Liu, Deborah Sheridan, Charles Wood

Nebraska Center for Virology: Faculty Publications

A cDNA clone of the bovine immunodeficiency-like virus (BW) trans-activator gene (tat) was identified and characterized. The tat cDNA clone was generated by splicing, and on the basis of sequence analysis, the Tat protein was found to be encoded entirely by the first exon. It is 103 amino acids in size and shares sequence homology with the human immunodeficiency virus (HW) Tat. The BIV tat clone can trans activate the BIV promoter effectively, as measured by the expression of the bacterial chloramphenicol acetyltransferase gene, when transfected into bovine cells. Besides activating the BIV promoter, the BIV Tat can also trans …

Kinetic Characterization Of A Recombinant C-Terminal Mutant Of Reverse Transcriptase From The Human Immunodeficiency Virus, Thomas S. Heard

Chemistry & Biochemistry Theses & Dissertations

The human immunodeficiency virus (HIV) reverse transcriptase (RT) (EC 2.7.7.49) is the central replication enzyme for HIV. In general, the kinetic mechanism for this and all other polymerases involves the ordered binding of two substrates: a primer-template (PT) followed by a deoxyribonucleoside triphosphate (dNTP). Previous investigations prompted this research when it was discovered that the substrate dNTP, in absence of PT, could protect a recombinant c-terminal mutant HIV-1 RT from inhibition by pyridoxal-5'-monophosphate (PLP), an active-site dNTP inhibitor. In contrast, the non-mutant recombinant HIV-1 RT required both substrates for protection from PLP inhibition. This investigation sought to determine if this …

Dual Regulation Of Silent And Productive Infection In Monocytes By Distinct Human Immunodeficiency Virus Type 1 Determinants, Howard Gendelman, Peter Westervelt, Timothy Henkel, David B. Trowbridge, Jan Orenstein, John Heuser, Lee Ratner

Nebraska Center for Virology: Faculty Publications

The regulation of human immunodeficiency virus type 1 infection and replication in primary monocytes was investigated by mutagenesis of recombinant proviral clones containing an env determinant required for the infectivity of monocytes. Virus replication was assayed by determination of reverse transcriptase activity in culture fluids and by recovery of virus from monocytes following cocultivation with uninfected peripheral blood mononuclear cells. Three virus replication phenotypes were observed in monocytes: productive infection, silent infection, and no infection. Incorporation of the monocytetropic env determinant in a full-length clone incapable of infection or replication in primary monocytes (no infection) conferred the capacity for highly …

Transformation Of A Continuous Rat Embryo Fibroblast Cell Line Requires Three Separate Domains Of Simian Virus 40 Large T Antigen., Jiyue Zhu, Philip W. Rice, Lisa Gorsch, Marina Abate, Charles N. Cole

Dartmouth Scholarship

Mouse C3H 10T1/2 cells and the established rat embryo fibroblast cell line REF-52 are two cell lines widely used in studies of viral transformation. Studies have shown that transformation of 10T1/2 cells requires only the amino-terminal 121 amino acids of simian virus 40 (SV40) large T antigen, while transformation of REF-52 cells requires considerably more of large T antigen, extending from near the N terminus to beyond residue 600. The ability of a large set of linker insertion, small deletion, and point mutants of SV40 T antigen to transform these two cell lines and to bind p105Rb was determined. Transformation …

Cytolytic T Lymphocytes Specific For Tumors And Infected Cells From Mice With A Retrovirus-Induced Immunodeficiency Syndrome., Jennifer G. Erbe, Kathy A. Green, Karen M. Crassi, Herbert C. Morse, W R. Green

Dartmouth Scholarship

LP-BM5 retrovirus complex-infected C57BL/6 mice develop immunodeficiency, somewhat analogous to AIDS, termed murine AIDS (MAIDS). After secondary stimulation with syngeneic B-cell lymphomas from LP-BM5-infected mice, C57BL/6 mice produced vigorous CD8+ cytotoxic T lymphocytes specific for MAIDS-associated tumors. An anti-LP-BM5 specificity was suggested because spleen and lymph node cells from LP-BM5-infected mice served as target cells in competition assays, and cells from LP-BM5, but not ecotropic, virus-infected mice functioned as secondary in vitro stimulators to generate cytotoxic T lymphocytes to MAIDS tumors.

Identification And Characterization Of A Human Herpesvirus 6 Gene Segment That Trans Activates The Human Immunodeficiency Virus Type 1 Promoter, Yunqi Geng, Bala Chandran, Steven Josephs, Charles Wood

Nebraska Center for Virology: Faculty Publications

Human herpesvirus 6 (HHV-6) is a lymphotropic herpesvirus, and in vitro, HHV-6 can productively infect many of the same cell types as can human immunodeficiency virus (HIV). Coinfection by both viruses in vitro can lead to both activation of the HIV promoter and acceleration of cytopathic effects. We have previously demonstrated that a large, 22.25-kb cloned HHV-6 fragment, pZVB70, can trans activate HIV promoter expression in vitro. In this study, we show that the pZVB70 fragment can trans activate the HIV promoter in human T-cell lines as well as in the monkey kidney cell line CV-1. The pZVB70 insert was …

The Inhibitory Effects Of The Extracts Of Zingiber Plants On The Adsorption, Growth, And Replication Of Phage Lpp-1 In Cyanobacterium, Ebby Paul Jido

Master's Theses

No abstract provided.

Altered Expression Of Adenovirus 12 Dna-Binding Protein But Not Dna Polymerase During Abortive Infection Of Hamster Cells, Lynne A. Lucher, Benjawan Khuntirat, Jiansheng Zhao, Peter C. Angeletti

Nebraska Center for Virology: Faculty Publications

Replication of human adenovirus type 12 DNA is blocked in abortively infected baby hamster kidney cells. The activity and accumulation of adenovirus 12 DNA polymerase is equivalent in infected hamster and human cell extracts. However, the accumulation of adenovirus type 12 DNA-binding protein is approximately 120-fold lower in extracts from infected hamster cells when compared to infected permissive human cells. This difference in accumulation is not because of replication of viral DNA during productive infection, since this difference is observed in the presence of hydroxyurea. The DNA-binding protein from infected hamster cells retains the ability to bind denatured DNA-cellulose. An …

The Ability Of Simian Virus 40 Large T Antigen To Immortalize Primary Mouse Embryo Fibroblasts Cosegregates With Its Ability To Bind To P53., Jiyue Y. Zhu, Marina Abate, Philip W. Rice, Charles N. Cole

Dartmouth Scholarship

The large T antigen encoded by simian virus 40 (SV40) plays essential roles in the infection of permissive cells, leading to production of progeny virions, and in the infection of nonpermissive cells, leading to malignant transformation. Primary mouse embryo fibroblasts (MEFs) are nonpermissive for SV40, and infection by wild-type SV40 leads to immortalization and transformation of a small percentage of infected cells. We examined the ability of an extensive set of mutants whose lesions affect SV40 large T antigen to immortalize MEFs. We found that immortalization activity was retained by all mutants whose lesions are located upstream of codon 346. …