Inhibition by methioninyl adenylate of focus formation by Rous sarcoma virus.

Methioninyl adenylate is a specific and potent inhibitor of the enzyme methionyl-tRNA synthetase and, consequently, of protein biosynthesis. In cultures of chick embryo fibroblasts infected with Rous sarcoma virus, incubation for a 2-day period with 1 to 3 mM concentrations of this inhibitor, as late as 4 days after infection, irreversibly prevented subsequent formation of foci of transformed cells. Later addition could also elicit the irreversible disappearance of already existing foci, by phenotypic reversion and/or cell killing. Virus production in transformed cells and replication in newly infected cells were also inhibited but to a lesser degree. Under the same conditions, the same concentrations of methioninyl adenylate caused only a reversible growth arrest of normal cells. The selective toxicity of the inhibitor for transformed cells is not due to a greater affinity for the target enzyme, but it may be due to the fact that inhibition of protein biosynthesis is only partially reversible in these cells, whereas it is fully reversible in normal cells.

Cooperation between the H-ras oncogene and a truncated derivative of the v-myb oncogene in transformation of hamster embryo fibroblasts.

The ras oncogenes alone fully transform established (immortalized) rodent fibroblasts in a few days, but generally transform early-passage fibroblasts only partially, unless their action is complemented by that of a nuclear, immortalizing, oncogene. Here we show that transfection of second-passage Syrian hamster embryo fibroblasts (HEFs) by the EJ-H-ras oncogene coupled to the neo gene, followed by selection with G418, gives rise to apparently normal, or only slightly transformed, clonal colonies, only a few of which become established. The study of two established clonal lines showed that they acquired only after some weeks, and stepwise, the main characteristics of full neoplastic transformation, i.e. anchorage independence, reduced requirement for serum growth factors and tumorigenicity. Later both clonal lines became increasingly tumorigenic and completely independent of exogenous growth and attachment factors, without increase in the expression of the H-ras oncogene. Transfection of one of the clones, early after its isolation, with a truncated derivative of the nuclear v-myb oncogene devoid of its transcriptional negative regulatory domain and able to partially transform chicken embryo fibroblasts [(myb(KXANM)] gave rise to more transformed cells, expressing both EJ-H-ras and myb(KXANM), which became tumorigenic earlier than the controls and remained more tumorigenic later on. With more efficient transfection techniques, numerous foci of fully transformed cells were subsequently obtained, in a few days, in cultures transfected sequentially with EJ-H-ras(neo) and myb(KXANM) and in cultures co-transfected with the two oncogenes. Highly tumorigenic, serum-independent and immortalized clones expressing both oncogenes were obtained from these cultures. Hence, the truncated myb(KXANM) oncogene accelerate the stepwise transformation of unestablished HEFs by the EJ-HH-ras oncogene and, together with this oncogene, fully transforms these same cells in a single step. The two oncogenes acting in cooperation also induce cell immortalization, but myb(KXANM), by itself, is not an immortalizing oncogene. No cooperation was observed between EJ-H-ras(neo) and the unaltered v-myb oncogene.

Differential codon usage for conserved amino acids: evidence that the serine codons TCN were primordial.

The availability of specialized sequence databanks for Escherichia coli, Saccharomyces cerevisiae and Bacillus subtilis made it possible to build a set of 105 protein-coding genes that are homologous in these three species. An analysis of the triplets at both the nucleotide and amino acid level revealed that the codon bias of some amino acids are significantly higher at conserved rather than at non-conserved positions. Comparisons of homologous genes in E. coli and Salmonella typhimurium, and in S. cerevisiae and Drosophila melanogaster, led to the same conclusion. A special case was made for serine in E. coli, whose major codon is AGC for non-conserved and TCC for conserved residues. We interpret this observation as evidence that the primordial codons for serine were TCN, while codons AGY appeared later. This conclusion is substantiated by an analysis of the codon usage of catalytic serine residues in ancient, ubiquitous and essential proteins (ATP synthases and topoisomerases). It is shown that in these proteins the proportion of the catalytic serine residues coded by TCN is significantly higher than the one expected from the overall codon usage of serine residues.

Evidence for horizontal gene transfer in Escherichia coli speciation.

After extracting more than 780 identified Escherichia coli genes from available data libraries, we investigated the codon usage of the corresponding coding sequences and extended the study of gene classes, thus obtained, to the nature and intensity of short nucleotide sequence selection, related to constraints operating at the nucleotide level. Using Factorial Correspondence Analysis we found that three classes ought to be included in order to match all data now available. The first two classes, as known, encompass genes expressed either continuously at a high level, or at a low level and/or rarely; the third class consists of genes corresponding to surface elements of the cell, genes coming from mobile elements as well as genes resulting in a high fidelity of DNA replication. This suggests that bacterial strains cultivated in the laboratory have been fixed by specific use of antimutator genes that are horizontally exchanged.

The origins of the strategy of codon use.

We analyzed the DNA sequences taking as an elementary pattern segments of increasing length from the codon to the gene. We have thus been able to identify part of the constraints from which originates the use of the code degeneracy in each gene. Our results show that the strategy of codon use is not solely related to the translation apparatus characteristics.

[Injuries to the upper tibial epiphysis. Apropos of 20 cases]. / Les traumatismes épiphysaires supérieurs du tibia. A propos de 20 cas.

The authors report 20 cases of injuries involving the proximal tibial epiphysis (16 avulsion fractures of the tibial tubercle, 4 epiphyseal fractures), occurring in adolescents engaged in athletics, in 3/4 of the cases. Sixteen displaced fractures needed open reduction and internal fixation with screw(s). Leg shortening (12 mm) occurred in a 14 year-old male with a displaced fracture of both the tibial tubercle and proximal epiphysis, in which premature ossification had taken place; fixation with Kirschner wires would have been the treatment of choice before closure of the tibial epiphysis. At follow-up, function was acceptable in all cases; all the patients had returned to full daily activity and no further surgical procedures were needed. Long-term knee laxity became obvious in one patient, however, with repeated fracture of the tibial tubercle. Associated ligamentous and meniscal tears should therefore be sought on early clinical examination and confirmed by arthroscopy or arthrotomy after surgical fixation.

[Teutschlaender lipo-calcino-granulomatosis or tumoral calcinosis of Inclan (author's transl)]. / Lip-calcino-granulomatose de Teutschlaender ou calcinose tumorale de Inclan

The present report describes a typical case of tumoral calcinosis. Differential diagnosis was initially directed towards sarcoma suggested by fibrous connective tissue surrounding cystlike cavities. The course of this disease led to chronic multiple fistulae with secondary infection in spite of two attempts of surgical excision. This case adds further support to the results of earlier reports showing no specific biological abnormalities. The present sutyd indicates otherwise that tumoral calcinosis and lipo-calcino-granulomatosis of Teutschlaender are the same condition. The pathogenesis of this affection remains enigmatic; there is no evidence that the lipidic excess should be the beginning of the process, but this disease must be considered as a distinctive form of calcinosis. The surgical exeresis is the only possible treatment, even if it doesn't prevent recurrence.

[Constraints acting on the base sequence in a polynucleotide. II. Distribution of complementary tetranucleotides in genes of Escherichia coli and bacteriophages lambda and T7]. / Etude des contraintes qui s'exercent sur la succession des bases dans un polynucléotide. II. La distribution des tétranucléotides complémentaires dans les gènes d'Escherichia coli et des bactériophages lambda et T7.

The complementary tetranucleotides tend to be equally favoured or avoid in E. coli, lambda and T7 genes. Constraints exist that act equally on nucleotide sequence of each one of both strings of DNA molecule, without any relation with the lecture phase.