Recent experiments have shown that gene amplification can be mediated by submicroscopic, autonomously replicating, circular extrachromosomal molecules. We refer to those molecules as episomes (S. Carroll, P. Gaudray, M. L. DeRose, J. F. Emery, J. L. Meinkoth, E. Nakkim, M. Subler, D. D. Von Hoff, and G. M. Wahl, Mol. Cell. Biol. 7:1740-1750. The experiments reported in this paper explore the way episomes are formed and their fate in the cell over time. The data reveal that in our system the episomes are initially 250 kilobases, but gradually enlarge until they become double minute chromosomes. In addition, we show that episomes or double minute chromosomes can integrate into chromosomes. Our results also suggest that episomes can be produced by deletion of the corresponding sequences from the chromosome.

Transferrin (Tf) is the major iron binding protein in vertebrate serum. It shares homologous amino acid sequences with four other proteins: lactotransferrin, ovotransferrin, melanoma antigen p97, and HuBlym-l. Antigen p97 and the Tf receptor genes have been mapped on human chromosome 3. The goal of the study described here was to initiate the characterization of the Tf gene by identifying and characterizing its cDNA and mapping its chromosomal location. Recombinant plasmids containing human cDNA encoding Tf have been isolated by screening an adult human liver library with a mixed oligonucleotide probe. Within the 2.3 kilobase pairs of TfcDNA analyzed, there is a probable leader sequence encoded by 57 nucleotides followed by 2037 nucleotides that encode the homologous amino and carboxyl domains. During evolution, three areas of the homologous amino and carboxyl domains have been strongly conserved, possibly reflecting functional constraints associated with iron binding. Chromosomal mapping by in situ hybridization and somatic cell hybrid analysis indicate that the Tfgene is located at q21-25 on human chromosome 3, consistent with linkage of the Tf, Tf receptor, and melanoma p97 loci.Transferrin (Tf) carries ferric iron from the intestine, reticuloendothelial system, and liver parenchymal cells to all proliferating cells in the body. The family of Tf-like proteins represents the product of an intragenic duplication followed by a series of independent gene duplications (1-4). Serum Tf (1), hen ovotransferrin (2, 3), lactotransferrin (4), melanoma antigen p97 (5), and a transforming protein from chicken lymphoma ChBlym-1 (6) share strong amino acid sequence homologies. A transforming protein from Burkitt lymphomas recently described (7) may also belong to the Tf family. There is also significant internal homology in the amino-terminal (NH2) and carboxyl-terminal (COOH) domains of Tf, lactotransferrin, and ovotransferrin (1-4). For example, the NH2 and COOH domains of human Tf reveal 40% identity when the NH2 domain (residues 1-336) and the COOH domain (residues 337-678) are compared (1). In the study described Screening of cDNA Clones. The cDNA library, kindly provided by Stuart H. Orkin (Harvard Medical School, Boston) was constructed from human liver RNA as described (10). The cDNA library was incubated overnight on L agar plates containing 10 jig of tetracycline per ml and was transferred to nitrocellulose filters. The plasmids were amplified with 250 ,tg of chloramphenicol per ml and the filters were prepared for hybridization as described by Grunstein and Hogness (11). The filters were hybridized at 37°C with 32P-labeled oligonucleotide mixed probes as described by Wallace, et al. (12). The hybridization mixture contained 0.9 M NaCl, 0.09 M Tris HCl (pH 7.5), 0.006 M EDTA, 0.5% NaDodSO4, Denhardt's (13) solution (5 x strength), 100 ,ug of denatured Escherichia coli DNA per ml, and 6.4 ng of 5' end-labeled oligonucleotide mixed probes per ml having a specific activity of -7 x 108 cpm/,ug.Preparation...

Recently, a new clinically recognizable syndrome resulting from a small interstitial deletion of 17p [del(17)(p11.2p11.2)] was described in ten unrelated patients. We have identified six additional patients with similar cytogenetic and phenotypic abnormalities. Consistent clinical manifestations include 1) brachycephaly with a broad face and nasal bridge, 2) flat midface, 3) short, broad hands, and 4) mental retardation associated with hyperactivity and often self-destructive behavior. The craniofacial and hand anomalies are reminiscent of several craniosynostosis syndromes. Most patients also had growth deficiency and several other (more variable) congenital malformations. Chromosome studies with special attention to 17 should be performed in any patient with a similar phenotype.

Patients with a partial deletion of the long arm of chromosome 10 are rare. We report eight new cases involving various segments of 10q: one terminal deletion (10q26), four (8;10) translocations resulting in terminal deletions (10q26) and duplications (8q24.3), a de novo interstitial deletion (10q23), an interstitial deletion due to a (10;13) translocation (10q11.2----10q22.1), and a ring (10p15----10q26).

Ceruloplasmin (CP) is a copper-binding protein in vertebrate plasma. It is the product of an intragenic triplication and is composed of three homologous domains. Oligonucleotide probes constructed according to published amino acid sequences were used to identify cDNA clones encoding human CP. Two clones, CP-1 and CP-2, differed from each other by the presence or absence, respectively, of a deduced sequence of four amino acids. The two clones provided 81% of the sequence encoding CP. Comparison of the nucleotides of the three domains of the CP coding sequence revealed internal domain homology with identity of sequences ranging from 50.1% to 56%. The nucleotide sequence of CP-2 cDNA was compared to that of a homologous human protein, clotting factor VIII, and was found to be 48% identical overall. The CP gene was mapped to human chromosome 3 by somatic-cellhybrid analysis and to 3q25 by in situ hybridization; however, sites of hybridization to DNA on other chromosomal sites suggested additional CP-like DNA sequences in the human genome. A DNA polymorphism was detected with CP cDNA after endonuclease digestion of human DNA by Pst I. CP mRNA was detected in human liver, macrophages, and lymphocytes by in situ histohybridization.