Nucleotide sequence of the simian virus 40 HindII + III restriction fragment I (fourth part of the T antigen gene)

Transforming genes and gene products of polyoma and SV40

The small DNA-containing viruses, SV40 and polyoma, transform cells in vitro and induce tumors in vivo. For both viruses two genes required for transformation have been found. The genes required for transformation are also involved in productive infection. Although the two viruses are similar in their effects on cells, the organization of the transforming genes and gene products is different. The purpose of this review is to compare what is known about the biology and the biochemistry of the early regions of the two viruses. The genetic and biochemical studies defining the sequences important for transformation will be reviewed. Then, the products of the transforming genes, called T antigens, will be discussed in detail. There is a substantial body of descriptive information on those products, and studies on the function of the T antigens have also begun.

Nucleotide sequence of the Hind-I-proximal part of simian virus 40 HindII + III restriction fragment B (fifth part of the T antigen gene)

The nucleotide sequence of the simian virus 40 DNA segment that lies between the HindIII restriction endonuclease cleavage site at map position 0.324 and the AtuI cleavage site at 0.261 has been determined by the base-specific partial chemical degradation procedure of Maxam and Gilbert. This region comprises 335 base pairs and represents 6.4% of the total SV40 genome and 41% of the restriction fragment Hind-B. It connects in the clockwise direction to the restriction fragment Hind-I (described in the preceding paper). Hind-B is situated in the second half of the early transcription region of the SV40 genome and encodes information (including the termination signal) for the early protein large-T antigen. in the part of Hind-B described here, the DNA strand that has the same polarity as early 19-S mRNA defines only one open reading frame for translation; the other two are blocked by multiple triplets corresponding to termination codons. The open reading frame is part of one that runs throughout much of the early region: from the second splicing boundary of the large-T gene (position 0.534) to the information for the large-T stop signal (position 0.174) near the Hind-B/Hind-G junction, and which together with the non-contiguous DNA segment from position 0.65 (site of the information for the large-T start signal) to 0.69 (the first splicing boundary) codes for the entire large-T antigen.

Nucleotide sequence of simian virus 40 DNA: structure of the middle segment of the HindII + III restriction fragment B (sixth part of the T antigen gene) and codon usage

We report here the nucleotide sequence of the simian virus 40 DNA region that lies between the EcoRII restriction endonuclease cleavage sites at map positions 0.214 and 0.281. The sequence was determined by partial chemical degradation of terminally labeled DNA fragments according to the procedure of Maxam and Gilbert. This region represents 6.7% of the SV40 genome and is located in the middle of HindII + III restriction fragment B. It is expressed as part of the early 19-S messenger RNA, which codes for the large-T antigen protein. Only one open reading frame for translation can be deduced from the message strand of the DNA and this reading frame connects in phase with the one of both neighboring fragments. This publication is the last in a series of papers about the T-antigen gene, and several properties of this gene and its product are discussed. The non-randomness of codon usage is similar to that previously discussed for the late part of the genome. Moreover, it appears that the choice of a third letter can be determined by the nature of the following codon; some codons which start with a pyrimidine are almost never preceded by an adenosine and some ANN-type codons are almost never preceded by a guanosine.

Nucleotide sequence of the simian virus 40 HindII + III restriction fragment I (fourth part of the T antigen gene)

The HindII + III restriction fragment I (Hind-I) from simian virus 40 DNA represents 4.96% of the genome and maps in the early transcription region. Hind-I is an internal segment of the A gene and its information is expressed as part of the early 19-S mRNA, which codes for T antigen. We report here the nucleotide sequence of the 259-base-pair Hind-I fragment. The sequence was determined and confirmed by RNA and DNA sequencing methods: by analysis of oligonucleotides resulting from T1 and pancreatic RNase digestion of labeled RNA transcribed from SV40 DNA with Escherichia coli DNA-dependent RNA polymerase, by partial degradation of RNA transcripts with snake venom phosphodiesterase, and by base-specific chemical degradation of 5'-end-labeled subfragments of Hind-I according to the procedure of Maxam and Gilbert. Multiple triplets corresponding to termination codons occur in two of the three reading frames of the DNA strand that has the same polarity as early mRNA. The open reading frame connects in phase with the one of the Hind fragments flanking Hind-I, and the amino acid sequence specified by Hind-I lies in the middle part of the large-T antigen. Some features of the primary nucleotide sequence and of early transcription are discussed.

Nucleotide sequence of the simian virus 40 HindII + III restriction fragment A (second part of the T antigen gene)

The nucleotide sequence of the second part of the simian virus 40 DNA HindII + III restriction fragment A is presented. The sequence extends from map position 0.533 to 0.424 and together with the first part of Hind-A [Volckaert et al. Proc. Natl Acad. Sci. U.S.A. 75, 2160--2164 (1978)] completes the total hind-A sequence, comprising 1169 base pairs. The second half of Hind-A includes the region corresponding to the second splicing boundary common to small tumor antigen (small-t) and large tumor antigen (large-T) mRNA and it contains coding information for an internal portion of large-T antigen. Two similar secondary structures of reasonable thermodynamic stability can be proposed for the nucleotide sequence of the pre-mRNA corresponding to the region reported here. Their possible relevance to the splicing of the SV40 early mRNAs is discussed. The deduced amino acid sequence is 188 residues long and contains a Lys-Lys-Lys-Arg-Lys-stretch which may be involved in the DNA binding capacity of large-T. A presumptive phosphorylation site is also present.