Complete amino acid sequence of the group-specific antigen gene-encoded phosphorylated proteins of mouse leukemia viruses

Stephan Oroszlan and the Proteolytic Processing of Retroviral Proteins: Following A Pro

Steve Oroszlan determined the sequences at the ends of virion proteins for a number of different retroviruses. This work led to the insight that the amino-terminal amino acid of the mature viral CA protein is always proline. In this remembrance, we review Steve’s work that led to this insight and show how that insight was a necessary precursor to the work we have done in the subsequent years exploring the cleavage rate determinants of viral protease processing sites and the multiple roles the amino-terminal proline of CA plays after protease cleavage liberates it from its position in a protease processing site.

The gag and pol genes of bovine leukemia virus: nucleotide sequence and analysis

The DNA sequence of the gag and pol regions of a provirus cloned from a bovine tumor is presented. In order to confirm these results the sequence of portions of a second clone, derived from a virus-producing cell line, was also determined. The gag gene was found to consist of 1179 nucleotides, which probably encode only three proteins: an N-terminal protein of 109 amino acids, a major core protein (p24) of 215 amino acids, and a nucleic acid binding protein (p12) of 69 residues. An open reading frame, whose translated product showed clear homology to the avian and murine proteases, was found beginning immediately upstream of the 3' end of gag. Following this protease region, a third long open reading frame, encoding 852 amino acids, showed clear homology to both avian and murine pol genes. The mechanism of translation of the protease and pol gene products cannot be predicted with certainty. Like Moloney murine leukemia virus (M-MuLV), BLV has a termination signal at the 3' end of gag, but unlike M-MuLV the protease is in a different reading frame. Like Rous sarcoma virus (RSV), BLV has a termination signal at the 3' end of the protease region and the reverse transcriptase is in a different (i.e., the third) reading frame. Possible translation mechanisms are discussed. Finally, the BLV gag and pol gene products are highly related to those of the human T-cell leukemia virus (HTLV); relatedness varied from 37% amino acid identities within the N terminal gag protein to 54% within the nucleic acid binding protein. Highly significant homology with both murine and avian type-C proteins was found within p24, p12, and the putative protease, reverse transcriptase, and endonuclease. Based on this homology, the BLV-HTLV family of viruses appears about equally distantly related to murine and avian type-C viruses.

Purification and chemical and immunological characterization of avian reticuloendotheliosis virus gag-gene-encoded structural proteins

Five gag-gene-encoded structural proteins, designated p12, pp18, pp20, p30, and p10 were purified from replication-competent avian reticuloendotheliosis-associated virus (REV-A) by high-performance liquid chromatography complemented with chloroform-methanol extraction and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Based on amino acid composition and NH2- and COOH-terminal sequence analysis p12, pp18, p30, and p10 are distinct from one another, whereas pp20 is likely identical to pp18 in primary structure. The p12 was resistant to Edman degradation and was found to be myristylated at the NH2-terminal amino group. Sequence comparisons among the retrovirus family show that pp18/pp20 and p10 are, respectively, homologs of phospho-proteins and nucleic acid-binding proteins. A comparison of terminal sequences with the nucleotide sequence of spleen necrosis virus (SNV) revealed that the gag genes of SNV and REV-A are highly conserved; together with the identification of REV-A gag-precursor polyprotein, Pr60gag in immunoprecipitates of radiolabeled cell lysates, this comparison also led to the establishment of the organization of Pr60gag, viz., NH2-p12-pp18-p30-p10-OH. Sequence comparisons show that REV-A/SNV is related to mammalian type C viruses: the pp18-p30 region is most homologous to the macaque/colobus group and least to simian sarcoma virus (SSV), whereas both the 5'- and 3'-gag regions (i.e., p12 and p10) are clostest to SSV. Immunological studies using monospecific antisera and Western-blot analysis showed that antigenic determinants of REV-A p30 are conserved in most of mammalian type C and type D viruses, but those of REV-A p12 are shared only with simian sarcoma-associated virus (SSAV) and endogenous viruses of macaques.

Onc genes and other new targets for cancer chemotherapy

Recent advances in molecular biology have raised the hope that understanding of human cancer might progress rapidly and that improvements in therapy might result (Bishop 1983a, b; Busch 1962; Busch 1976; Duesberg 1983). With the development of gene cloning, DNA sequence analysis and improved hybridization methods, it became possible to evaluate whether cancer results from alteration in gene dosage, point or multiple mutation of genes, translocations, deletions, insertions, inversions, cis or trans altered promoters, amplification, and a variety of other genetic factors, including enhancer elements that alter rates of readouts of particular mRNA species. "Onc genes" are under intensive study because they offer manageable probes for evaluation of these various possibilities and also because the study of their cellular analogs may further understanding of the molecular biology of normal fetal and malignant cells. Despite the excessive enthusiasm of some proponents of this field and the negativism of its critics (Bishop 1983 a, b; Duesberg 1983), it is clear that analytical tools and new information will be of value in further studies on experimental cancer, regardless of whether cellular oncogenes (c-onc genes) have anything to do with human cancer or not. In the meantime, studies on enzymes, proteins and epitopes involved in growth processes, have opened new avenues for inhibition of human cancer by quantitative reduction of biosynthetic reactions.

Complete amino acid sequence of the nucleic acid-binding protein of bovine leukemia virus

The complete amino acid sequence of the nucleic acid-binding protein p12 of bovine leukemia virus (BLV) has been determined. Peptides were generated by enzymatic digestion and formic acid cleavage, purified by reversed-phase liquid chromatography and subjected to automated Edman degradation. BLV p12 is a proline-rich linear polypeptide composed of 69 amino acids with Mr 7558. A comparison of the p12 structure to that of the avian and murine type C retroviral nucleic acid-binding proteins shows significant homology only in the putative binding domain. This conserved region is duplicated BLV p12 as in the avian homolog.