tpr homologues activate met and raf.

We have previously described the primary structure of the entire met domain and part of the tpr domain present in the human tpr-met oncogene. The isolation and sequencing of an additional cDNA clone now enables us to present the complete primary sequence of the tpr domain. A computer search has unearthed a remarkable identity between tpr and a rat sequence found at the 5-prime end of the activated raf oncogene. The occurrence of tpr-like sequences in combination with two oncogenes suggests that tpr contributes a domain(s) relevant to the observed activation of met and raf.

Activation of the met oncogene in the human MNNG-HOS cell line involves a chromosomal rearrangement.

In this study it is demonstrated that the activated met gene, which was originally detected in the MNNG-HOS chemically transformed human cell line, is a chimeric gene formed by the joining together of two distinct regions of DNA. Rearrangement of cellular DNA in MNNG-HOS cells was demonstrated by Southern analyses, which showed that the MNNG-HOS cell line contained unique met-related DNA fragments that were not detected in the parental cell line, HOS. Chromosomal localization using a series of rodent-human hybrid cell lines showed that the 5' end of the activated met gene is derived from human chromosome 1, in contrast to the 3' end of met which has been previously localized to human chromosome 7. The chimeric gene is transcribed to produce a 5-kb mRNA that is encoded both by regions of the gene derived from chromosome 1 and by regions of the gene derived from chromosome 7. Karyotype analysis of HOS and MNNG-HOS cells has identified several marker chromosomes that involve translocations of chromosomes 1 and 7. The possible location of the activated met locus within these rearranged chromosomes is discussed.

Ribosomal protein S6 phosphorylation and morphological changes in response to the tumour promoter 12-O-tetradecanoylphorbol 13-acetate in primary human tumour cells, established and transformed cell lines.

The phosphorylation of ribosomal protein S6 in fibroblasts, primary human tumour cells, established and SV40-transformed human cell lines was compared after the addition of 12-O-tetradecanoylphorbol 13-acetate (TPA). In fibroblasts and primary tumour cell cultures, stimulation of S6 phosphorylation was about 4-6-fold. Established and transformed cell lines showed enhanced S6 phosphorylation which was not further stimulated by the addition of TPA. These findings indicated that the influence of TPA on the metabolic pathway, that finally leads to the phosphorylation of protein S6 in cells with a limited lifespan (fibroblasts, primary human tumour cells) can be mimicked by unknown steps also associated with immortalization (establishment function) and the transformed state of the tumour cells. Another interesting observation were morphological changes of the established and SV40-transformed cells which were visible as early as 20 min after the addition of TPA. In fibroblasts and primary tumour cells no changes in morphology were observed, even after 8h incubation.