Maurice Cohen

ERV3, a Full-Length Human Endogenous Provirus: Chromosomal Localization and Evolutionary Relationships

A full-length human endogenous provirus termed ERV3 was isolated from a human fetal recombinant DNA library by low stringency hybridization with two probes: baboon endogenous virus LTR; and a pol-env subclone from the endogenous chimpanzee provirus, CH2. DNA sequencing within the clone and comparisons with other retroviruses revealed that ERV3 contains gag and pol gene sequences that are significantly related to those of mammalian type C retroviruses and previously described human endogenous proviruses. The ERV3 genome was determined to reside at a single locus on human chromosome 7 using a panel of rodent X human somatic cell hybrids.

Sequence arrangement of tRNA genes on a fragment of drosophila melanogaster DNA cloned in E. coli

A plasmid with the vector Col E1 attached to an insert of Drosophila melanogaster DNA carrying four tRNA genes has been cloned in E. coli. Some features of the sequence arrangement and the positions of the tRNA genes have been determined by electron microscopic methods and by restriction endonuclease mapping. tRNA genes were mapped at 1.4, 4.7, 5.9 and 8.6 kb from one of the Drosophila/Col E1 junctions in the Drosophila insert of total length 9.34 kb. There are several secondary structure features consisting of inverted repeat sequences of length about 70-100 nucleotide pairs, some with and some without intervening loops, irregularly distributed on the insert. Cross-hybridization of tRNAs isolated by hybridization to separated restriction fragments indicate that the tRNA genes at 4.7, 5.9 and 8.6 kb are identical and differ from the one at 1.4 kb. Thus the positions of the genes, of the secondary structure features and of the restriction endonuclease sites all indicate that the spacers between the genes are not identical tandem repeats. In situ hybridization with cRNA transcribed from the plasmid showed localization at region 42A of chromosome 2R.