Environmental and Molecular Mutagenesis - Legacy Tobacco ...

Tradescantia-Micronucleus (Trad-MCN) bioassay is an efficient test for genotoxioity
of environmental pollutants . It is currently under the validation prooess for the
International Program on Chemical Safety, WHO, UN for possible world-wide adoption for
chemical testing . Large population of Tradescantia clone #4430 has been vegetatively
propagated in the field and greenhouse in Guangxi Institute of Botany where the
climate and day length are suitable for the natural growth of this plant all year
round . Our Institute could serve as the supply house of this plant material for all
corners of the world . In order to maintain the genetic purity of this plant during
long distance shipping and rapid propagation of a large quantity, we developed a
practical technique to meet thie demand . First, young plant buds (usually whitish in
color and about 0 .5 cm long) which are beneath the soil surface are selected from the
low background stocks . The selected buds are then transplanted in a sterile
pollutant-free medium in a container and kept in the dark for shipping . These plant
buds can be kept alive in the shipping package for as long as a month duration . The
plant buds will turn into normal green plantlets after exposure to the light and ready
to be transplanted into field or greenhouse . The new plants will reach maturity Sn
about a month . The plants shipped in this fashion could minimize the possible genetic
change during shipping and gain easy passage of quarantine stations at the
international boundaries .
102
A NEW TW0-DINENTIONAL ANALYSIS OF DNA FRAGMENTS : TEMPERATURE GRADIENT GEL
ELECTROPHORESIS . Y .Chen, J .Fu, G .FAN, and B .Liu . Vest China University of
Medical Sciences . Chengdu, Sichuan (China)
A new technique, nased teeperature gradient gel electrophoresis (TGGE) .
used for sequence dependent separation of DNA fragments has been developed .
If double helical DNA is partially ∎elting in polyacrylamide gels, its
electrophoretic ∎obility undergoes a sharp transition, resulting in a
large reduction in ∎obility . In the present experiment, the transition that
was effected at a uniform concentration of denaturant, formamide . in a
temperature gradient formed during elect.rophoresis . Each restrictive
fragment of pBR322-DNA and bacteriaphage lambda-DNA exhibited the ∎obility
transition at a particular temperature . The sudden retardation of fragments
moving forward in the gel depended upon nucteotide composition and sequence .
rather than the length . When combined with length dependent electrophoresis
in the perpendicular direction . TGGE provided a two dlsentional separation
of DNA restrictive fragments . The resolving power of the new system was
demonstrated by the clear resolution of over 80 fragments of the restrictive
entyme Hinfl digest of lambda-DNA . This technique would find its appiic:ation
in ∎any fields .
103
RADICAL-MEDIATED SITE-SPECIFIC CROSSLINKING OF NUCLEAR MATRIX PROTEIN AND DNA . S .M .
Chiu, L .Y . Xue, L .R. Friedman, and N .L . ole nick . Departments of Radiology and
Environmental Health Sciences, Case Western Reserve University, Cleveland, ON (USA) .
Ionizing radiation-induced DNA-protein crosslinks (DPC), as assayed by
nitrocellulose filter-binding, are formed preferentially between domains of mammalian
chromosomal DNA enriched in active sequences and normal DNA-binding proteins of the
nuclear matrix (Chiu et al ., Radiat . Res . 107, 24 . 1986). In an effort to explore the
mechanism for the microheterogeneity, we have fractionated V79 cells and nuclei both
before and after irradiation. When intact cells were irradiated, the same radiation
dose response was obtained if the assay of DPC was subsequently conducted on cells,
nuclei, or nuclear matrix, suggesting that all of the components of DPC are retained
in the nuclear matrix. The same result was obtained for irradiation of nuclei and
assay of nuclei or nuclear matrix . However, the formation of DPC reached an early
maximum when nuclear matrix wae irradiated . Nuclear matrix was isolated by extraction
with lithium diiodosalicylate (LIS) . A. analyzed by SDS-PAGE, a similar set of
proteins was found in matrices prepared by LIS or by extraction in 2 N NaCl. In the
case of LIS extraction, nuclei were first stabilised by incubation in 0 .5 ∎M Cu804 .
The radiation dose-response for formation of DPC in these nuclei was 4-6 timea greater
than in untreated nuclei . Tests for the presence of Cu++ or other trace metals and
for the participation of Fenton-type teactions suggest a poseible explanation for the
selective formation of DPC at nuclear matrix sites, i .e ., the generation of hydroxyl
radicals or other oxidative radicals in the vicinity of preferential sites of binding
of metal ions . (Supported by NIH Grants RO1CA15378 and P30CA43703 .)
104
ISOLATION AND PARTIAL CHARACTERIZATION OF RAD4 GENE OF Saccharomyces cerevlsiae THAT
CAN BE PROPAGATED IN S .coli WITHOUT INACTIVATION . I .S .Choi, J .B .Kim, and S .D .Park,
Department of Zoology, College of Natural Sciences . Seoul National University, Seoul
151-742, South Korea
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
1989 EMS Abstracts
Notes
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