We have characterized two previously cloned genes, F1 and F2 (1) that code for elongation factor EF - 1 alpha of Drosophila melanogaster. Genomic Southern blot hybridization revealed that they are the only gene copies present. We isolated cDNA clones of both transcripts from embryonal and pupal stage of development that cover the entire transcription unit. The 5' ends of both genes have been determined by primer extension and for F1 also by RNA sequencing. These start sites have been shown to be used consistently during development. Comparison of cDNA and genomic sequences revealed that EF - 1 alpha,F1 consists of two and EF - 1 alpha,F2 of five exons. The two described elongation factor genes exhibit several regions of strong sequence conservation when compared to five recently cloned eucaryotic elongation factors.

At least 70% of human neuroblastomas display cytogenetically visible aberrations in the short arm of chromosome 1. We have used a panel of probes detecting polymorphic DNA loci, most of which were derived from a library of microdissected distal 1p chromosome fragments, to compare the hybridization pattern of DNA on nine different tumors and the corresponding normal tissue. In eight of the neuroblastomas allelic loss was observed with at least two probes. The deletions were of different size. Since a consensus deletion in all eight tumors included the segment 1p36.1-2, we conclude that genetic information related to neuroblastoma tumorigenesis is located within this approximately 10 megabase segment. Previous studies have revealed the amplification of MYCN in neuroblastomas. Our study did not provide evidence for a correlation between MYCN amplification and the 1p deletion, suggesting that the two genetic alterations result from molecular mechanisms that are not directly related to each other.

Proteins encoded by the proto‐oncogenes c‐myc, L‐myc, and N‐myc contain at their carboxy‐terminus a tripartite segment comprising a basic DNA binding region (BR), a helix‐loop‐helix (HLH) and a leucine zipper motif (Zip), that are believed to be involved in DNA binding and protein‐protein interaction. The N‐Myc oncoprotein is overexpressed in certain human tumors that share neuroectodermal features due to amplification of the N‐myc gene. Using a monoclonal antibody directed against an N‐terminal epitope of the N‐Myc protein in immunoprecipitations performed with extracts of neuroblastoma cells, two nuclear phosphoprotein, p20/22, forming a hetero‐oligomeric complex with N‐Myc are identified. Both proteins are phosphorylated by casein kinase II in vitro. By partial proteolytic maps we show that p20 and p22 are structurally related to each other and that p20 is identical with Max, a recently described in vitro binding partner of myc proteins. Time course experiments show the presence of the complex in cellular extracts immunoprecipitated within a 5 min interval after the preparation of the cell extract. While the expression of N‐myc is restricted, expression of both Max(p20/22) and the murine homolog Myn(p20/22) was observed in cells of diverse human and murine embryonal lineages as detected by heterologous complex formation. By introduction of expression vectors containing the wild type N‐myc gene or N‐myc genes with in frame deletions or point mutations into recipient cells and subsequent immunoprecipitation of the resulting N‐Myc proteins we show that the HLH‐Zip region is essential to the formation of the N‐Myc‐p20/22 complex.