The Saccharomyces cerevisiae Helicase Rrm3p Facilitates Replication Past Nonhistone Protein-DNA Complexes

In man, the specific chromosome that carries each of about 210 gene loci is known. These loci include at least one assigned to each chromosome (including the Y), about 110 assigned to specific autosomes, and about 100 to the X chromosome. For many loci, information on regional chromosomal localization is also available. The information comes mainly from studies in families and somatic cell hybrids, as well as an intgratsight of results from the two methods. Knowledge of the chromosome map gives insight into evolution, chromosomal organization in relation to genetic control mechanisms, and the pathogenesis of neoplasms and malformations. Furthermore, it is useful in prenatal or premorbid diagnosis of hereditary diseases.

https://science.sciencemag.org/content/sci/196/4288/390.full.pdf

The status of the gene map of the human chromosomes

Human and higher primate chromosomes have been compared by general and regional banding methods, including hybridization in situ. The general banding patterns of the chromosomes of gorilla, chimpanzee, and orangutan, but not gibbon, are similar to those of the human. Preliminary results show that chromosomes with similar banding patterns in different species often carry the same genes. Repetitious DNA's have undergone changes in structure and distribution which are reflected in changes in the regional banding patterns. These studies confirm that the evolutionary distance between the gibbon and the orangutan is relatively great compared to the distance between the orangutan and the other great apes, and suggest that man is more closely related to the gorilla than to the chimpanzee.

https://science.sciencemag.org/content/sci/198/4322/1116.full.pdf

Evolution of primate chromosomes

Human cytomegalovirus (HCMV) is the major viral cause of birth defects and a serious problem for immunocompromised individuals. Here we show that infection of cells with HCMV during the S-phase of the cell cycle results in two specific chromosome 1 breaks at positions 1q42 and 1q21. We demonstrate that purified virions, and not infected cell supernatant alone, are responsible for the damage. In addition, we show that the specific breaks occur when different sources of fibroblasts and strains of HCMV are used. Incubation of the virus with neutralizing antibody prevents the induction of breaks. However, UV-inactivated virus is as efficient as untreated virus in inducing specific damage to chromosome 1. Thus, there is a requirement for viral adsorption/penetration, but not new viral gene expression. This HCMV-mediated induction of site-specific damage in actively dividing cells may provide clues for the development of neurological defects in the congenitally infected infant.

https://www.pnas.org/content/pnas/97/2/853.full.pdf

Specific chromosome 1 breaks induced by human cytomegalovirus.

U2 RNA is one of the abundant, highly conserved species of small nuclear RNA (snRNA) molecules implicated in RNA processing1. As is typical of mammalian snRNAs, human U1 and U2 are each encoded by a multigene family. In the human genome, defective copies of the genes (pseudogenes) far outnumber the authentic genes2. The majority or all of the 35 to 100 bona fide U1 genes3–5 have at least 20 kilobases (kb) of nearly perfect 5′ and 3′ flanking homology in common with each other4,6; these U1 genes are clustered loosely in chromosome band 1p36 (refs 5, 7) with intergenic distances exceeding 44 kb. In contrast, the 10 to 20 U2 genes are clustered tightly in a virtually perfect tandem array which has a strict 6-kb repeating unit8,9. We report here the assignment, by in situ hybridization, of the U2 gene cluster to chromosome 17, bands q21–q22. Surprisingly, this region is one of three major adenovirus 12 modification sites which undergo chromosome decondensation (‘uncoiling’) in permissive human cells infected by highly oncogenic strains of adenovirus10,11. The two other major modification sites, 1p36 and 1q21, coincide with the locations of U1 genes5,7 and class I U1 pseudogenes12, respectively. We suggest that snRNA genes are the major targets of viral chromosome modification.

P. Szabo

Papers

Adenovirus 12 uncoiler regions of human chromosome 1 in relation to the 5S rRNA genes.