Amplification of a long sequence that includes a processed pseudogene for elongation factor 2 in the mouse

Genomic differentiation of 18S ribosomal DNA and beta-satellite DNA in the hominoid and its evolutionary aspects

The chromosome localization of two human multisequence families, rDNA and beta-satellite (beta-sat) DNA, was determined in humans and apes using double color fluorescence in-situ hybridization. Both DNA probes showed a distinct hybridization pattern with species-specific variations in hominoids. The stepwise differentiation of the integration, amplification, multilocalization, and reduction of the DNAs were observed interspecifically through the seven species examined. The stepwise events allowed us to trace back a phylogenetic divergence of the hominoid at the cytogenetic level. The manifestation of the events revealed that variations of the Y chromosome and acrocentric autosomes were synapomorphic characters in the divergence and those of metacentric autosomes were autapomorphic characters. Multilocalization of rDNA in the hominoid could also be interpreted as a result of translocations in terms of hetero-site crossover followed by a centric fission and formation of an acrocentric chromosome. Based on the observed rearrangements of rDNA and beta-sat DNA, we propose the following chromosomal phylogenetic divergence order in hominoids: gibbon-siamang-orangutan-gorilla-human-chimpanzee-bonobo. Our data provide additional evidence that evolution of the hominoid can be effectively studied using cytogenetic approaches.

Variable aberrant cDNAs in single diphtheria toxin-resistant human fibroblasts

We treated transformed human fibroblasts with diphtheria toxin (DT) and isolated 40 single cells that were toxin resistant but unable to propagate. In 13 of them toxin resistance was associated with the presence of one or more aberrant transcripts of the structural gene for elongation factor 2 (EF-2). cDNA obtained from these transcripts had 164-447 bp-long deletions. Each of these deletions was associated with 2-8 base pairs-long repeats at its breakpoints. Only 10 out of 16 cDNA deletions were associated with presumed exon junctions. A role is suggested for errors in transcription in producing the aberrant transcripts which gave rise to the deletion-bearing cDNA species.

The mouse elongation factor-2 gene: isolation and characterization of the promoter

Elongation factor 2 (EF-2) is a protein involved in peptide chain elongation in eukaryotes. We isolated the mouse EF-2 gene and characterized its promoter. We showed that the majority of enhancer elements were located within 500 bp of the flanking sequence and identified a factor binding site sequence (CGTCACGTGACGC) located between nucleotides -58 and -47 containing two CGTCA motifs separated by two nucleotides. The motif represents a half-site for binding of the cAMP response element (CRE) binding protein (CREB). Mutation analysis indicated that the presence of one CGTCA site alone conferred cAMP inducibility, but the presence of one or two CGTCA sites and spacing nucleotides elicited cAMP-independent, constitutive expression. UV cross-linking and DNA affinity chromatography revealed that three 40-, 43-, and 65-kD proteins bound to the CRE-like element. Of these, the 65-kD protein was unique to the CRE-like element. The 40-kD protein was ATF1 and the 43-kD protein with the molecular size of CREB was not CREB, on the basis of reactivity to their respective antibodies. Because ATF1 responds poorly to cAMP induction, it is likely the contributor to the constitutive expression rather than inductive expression of the CRE-like element, and, thus, the EF-2 gene.

A palindromic structure in the pericentromeric region of various human chromosomes

The primate-specific multisequence family chAB4 is represented with approximately 40 copies within the haploid human genome. Former analyis revealed that unusually long repetition units ( > 35 kb) are distributed to at least eight different chromosomal loci. Remarkably varying copy-numbers within the genomes of closely related primate species as well as the existence of human specific subfamilies, which most probably arose by frequent sequence exchanges, demonstrate that chAB4 is an unstable genomic element, at least in an evolutionary sense. To analyze the chAB4 basic unit in more detail we established a cosmid contig and found it to be organized as inverted duplications of approximately 90 kb flanking a noninverted core sequence of approximately 60 kb. FISH as well as the analysis of chromosome-specific hybrid cell lines revealed a chromosomal localization of chAB4 on chromosomes 1, 3, 4, 9, Y, and the pericentromeric region of all acrocentrics. Furthermore, we can detect chAB4 sequences together with alpha satellites, beta satellites, and satellite III sequences within a single chromosome 22-specific YAC clone, indicating that chAB4 is located in close proximity to the centromere, at least on the acrocentrics. Hence, chAB4 represents an unstable genomic structure that is located just in the chromosomal region that is very often involved in translocation processes.

The gene coding for the alpha 1 subunit of the skeletal dihydropyridine receptor (Cchl1a3 = mdg) maps to mouse chromosome 1 and human 1q32

Using both chromosomal in situ hybridization and molecular techniques, we report the genetic localization of the gene coding for the alpha 1 subunit of the skeletal slow Ca2+ current channel/DHP receptor gene (Cchl1a3) on human Chromosome (Chr) 1 (1q31-1q32 region) and on mouse Chr 1 (region (F-G)). On the basis of single-strand conformation polymorphism (SSCP-PCR) analysis in an interspecific backcross, we have determined that the Cchl1a3 = mdg (muscular dysgenesis) locus is very closely linked to the myogenin (Myog) locus.

The amplified long genomic sequence (ALGS) located in the centromeric regions of mouse chromosomes

We reported previously that the haploid genome of standard strains of laboratory mice contains approximately 70 copies of an amplified long genomic sequence, designated ALGS, that includes a retroposon of the gene for elongation factor 2 (MER). The length of each repeating unit is more than 60 kb, and the sequence of the unit is highly conserved among the repeats. In the present study, Southern blot analysis of the genomes of wild rodents demonstrated that the ALGS is present in all subspecies of Mus musculus and is abundant in M. spicilegus, whereas it is absent in M. spretus as well as in Rattus and other closely related genera. This result indicates that the amplification occurred after the species differentiation with the genus Mus and at least prior to the differentiation of subspecies of M. musculus. To locate chromosomal positions of the ALGS, in situ hybridization was carried out with laboratory strains and wild mice. It appears that the ALGS is located in the centromeric regions of most chromosomes in laboratory mice, M. musculus and M. spicilegus, whereas no positive signals were observed with M. spretus, in accordance with the results from the Southern blotting analysis.

A long-range repeat cluster in chromosome 1 of the house mouse, Mus musculus, and its relation to a germline homogeneously staining region

The laboratory mouse C57BL genome contains about 50 copies of a long-range repeat DNA family clustered in the C-D region of chromosome 1. The repeat length is more than 50 kb and includes sequences homologous to at least two mRNAs. There are small differences in the copies of this repeat family such as restriction site mutations and gross differences like rearrangements and insertions of LINE1 elements. A germline homogeneously staining region occurring as a chromosome 1 polymorphism in many feral populations of the house mouse is an amplified version of this long-range repeat cluster.