Chromosomal damage induced by human adenovirus type 12 requires expression of the E1B 55-kilodalton viral protein

Abstract

Infection of human embryonic kidney cells with adenovirus type 12 results in the induction of damage at specific (17q21-22, lp36, 1q21, and lq42-43) and random sites in the cellular chromosomes. A previous study by Durnam et al. (D. M. Durnam, P. P. Smith, J. C. Menninger, and J. K. McDougall, Cancer Cells 4:349-354, 1986) indicated that the expression of viral early region 1 (El) is sufficient for the induction of damage at band 17q21-22. In the present report we used an adenovirus type 12-adenovirus type 5 recombinant with ElA hybrid sequences as well as viruses with mutations in the adenovirus type 12 E1B genes to map adenovirus type 12 El functions involved in the induction of genetic damage. Our results show that the expression of the ElA proteins is not sufficient for this effect. On the other hand, mutations within the ElB 55-kilodalton protein but not the ElB 19-kilodalton protein affect the ability of the virus to induce both specific and random chromosomal damage.

Viral induction of site‐specific chromosome damage

“…The fourth fragile site, PSU1, which maps at 1q21, contains a family of U1 snRNA pseudogenes that are not transcribed as stable RNAs [8,14]. Of these sites, the RNU2 locus at 17q21-22 appears to be the most susceptible to Ad-induced fragility in a number of cell lines [4][5][6]11,15]. Virus-induced fragility at 1q42-43 is the least common and has mainly been observed in primary human embryonic kidney cells [5].…”

“…Given the genetic complexity of the E1 region of Ad, it was important to define which gene product(s) were necessary for the virus-induced chromosome fragility. Schramayr et al [15] demonstrated that the Ad12 E1B 55 000 protein is the E1 gene product necessary for the induction of specific fragility at both 17q21-22 and 1p36. The next step was to identify what cellular functions might also be involved.…”

“…It is clear from the studies on Ad described above that the viral E1B protein is required for induction of damage in infected cells. In fact, E1B alone can actually induce damage independently of viral infection [15,32]. In addition, the specific damage by HSV, including the uncoiling of chromosome 1q12-21 and the pericentric regions of chromosomes 9 and 16 as well as the pulverisation of chromosomes, requires viral protein synthesis.…”

Adenovirus Type 12-Induced Fragility of the Human RNU2 Locus Requires p53 Function

“…The four Ad12 chromosome "modification" sites were subsequently found to colocalize with four tandemly repeated multigene families (6,49,50,73): the human U1 small nuclear RNA (snRNA) genes at 1p36 (the RNU1 locus), the U2 snRNA genes at 17q21-22 (RNU2), an ancient family of U1 snRNA pseudogenes at 1q12-q22 (PSU1), and the 5S rRNA genes at 1q42-43 (RN5S). Ad12 efficiently induces fragility of the RNU1, RNU2, and PSU1 loci in several different cell lines (4,16,20,42,67); RN5S fragility has not been visualized except in primary human embryonic kidney cells (94) and may be weak, cell type specific, or abolished by immortalization. Colocalization of the four Ad12-inducible fragile sites with highly transcribed, tandemly repeated multigene families encoding small, abundant structural RNAs suggested that concentrated transcriptional activity might somehow interfere with local chromatin condensation (49); however, it was puzzling that none of the four modification sites appeared to be constitutively fragile in the absence of viral infection, and it was not known what viral or cellular functions were required to induce fragility.…”

“…It has been known for 30 years that infection of human primary embryonic kidney cells at a low multiplicity with adenovirus type 12 (Ad12), but not adenovirus 2 or 5, induces four sites of metaphase chromosome fragility (94); at a higher multiplicity both viruses induce generalized chromosome fragility (67,94). The four Ad12 chromosome "modification" sites were subsequently found to colocalize with four tandemly repeated multigene families (6,49,50,73): the human U1 small nuclear RNA (snRNA) genes at 1p36 (the RNU1 locus), the U2 snRNA genes at 17q21-22 (RNU2), an ancient family of U1 snRNA pseudogenes at 1q12-q22 (PSU1), and the 5S rRNA genes at 1q42-43 (RN5S).…”