Transfection of embryo fibroblasts by a human ras oncogene does not convert them into tumour cells unless the fibroblasts are established and immortalized before transfection. The embryo fibroblasts become tumorigenic if a second oncogene such as a viral or cellular myc gene or the gene for the polyoma large-T antigen is introduced together with the ras gene.

Tumorigenic conversion of primary embryo fibroblasts requires at least two cooperating oncogenes.

The DNA sequence of 168 promoter regions (-50 to +10) for Escherichia coli RNA polymerase were compiled. The complete listing was divided into two groups depending upon whether or not the promoter had been defined by genetic (promoter mutations) or biochemical (5' end determination) criteria. A consensus promoter sequence based on homologies among 112 well-defined promoters was determined that was in substantial agreement with previous compilations. In addition, we have tabulated 98 promoter mutations. Nearly all of the altered base pairs in the mutants conform to the following general rule: down-mutations decrease homology and up-mutations increase homology to the consensus sequence.

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Compilation and analysis of Escherichia coli promoter DNA sequences.

Internal duplication and homology with bacterial transport proteins in the mdr1 (P-glycoprotein) gene from multidrug-resistant human cells

In vitro insertional mutagenesis with a selectable DNA fragment

The oncogene of the human EJ bladder carcinoma cell lines arose via alteration of a cellular proto-oncogene. Experiments are presented that localize the genetic lesion that led to activation of the oncogene. The lesion has no affect on levels of expression of the oncogene. Instead, it affects the structure of the oncogene-encoded protein.

Mechanism of activation of a human oncogene.

DNA sequence analysis of the transposon Tn3: three genes and three sites involved in transposition of Tn3.

The transforming protein of Kirsten murine sarcoma virus (Ki-MuSV) is a virally encoded 21-kilodalton protein called p21 kis. The sequences encoding p21 kis were genetically localized to a 1.3-kilobase segment near the 5' end of the viral genome by assaying the capacity of a series of defined deletion mutants of molecularly cloned Ki-MuSV DNA to induce focal transformation of mouse cells. Nucleotide sequencing of a portion of this region has led to the identification of an open reading frame of 567 nucleotides coding for p21 kis protein.

Nucleotide Sequence of the Oncogene Encoding the p21 Transforming Protein of Kirsten Murine Sarcoma Virus

Heteroduplex mapping of small plasmids derived from R-factor R12: in vivo recombination occurs at IS1 insertion sequences.

Rl and R100 are large complex plasmids, approximately 90 kb in size, that code for multiple antibiotic resistance and functions involved in conjugal transfer of plasmid DNA.1,2 Both Rl and R100 belong to the FII plasmid incompatability group,3 indicating that the control of DNA replication in these plasmids is similar. Heteroduplex studies have confirmed this relationship by showing that the regions of Rl and R100 that are required for autonomous DNA replication have great sequence homology.4 This region is about 2.5 kb in length for R100, and, in addition to the replication origin,5,6,7 encodes at least one function that is required for replication. Part of this 2.5 kb replication region also encodes functions involved in plasmid incompatibility and copy number control.6 Studies with Rl have led to very similar conclusions.8

Eiichi Ohtsubo

Papers

DNA sequence analysis of the transposon Tn3: three genes and three sites involved in transposition of Tn3.

Nucleotide Sequence of the Oncogene Encoding the p21 Transforming Protein of Kirsten Murine Sarcoma Virus

Heteroduplex mapping of small plasmids derived from R-factor R12: in vivo recombination occurs at IS1 insertion sequences.

Structure and Function of the Replication Origin Region of the Resistance Factors R100 and R1

A genetic analysis of the transposon tn3: evidence for cointegrates as intermediates in transposition