Environmental and Molecular Mutagenesis - Legacy Tobacco ...

208 1989 EMS Abstracts
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
NOteS- 'were either hemfa`ygoSs or heterozygous at this gene locus . The calmodulin
antagonist, W13, at concentrations between 20 and 40 uM increased mutation in
the aprt gene of_tIffig,Epzygous CHO cell line, D423, several fold over that
observed with bleomycin alone . The analysis of this drug interaction and preliminary
characterization of the specificity of these mutants will be
presented .
603 -
DNA REPAIR IN HIGHER PLANTS . J .Velemfnskjr, Institute of Experimental Botany,
Czechoslovak Academy of Sciences, Vltavskd 17, 150 00 Praha 5,Czechoslovakia
.
Since 1972 several repair pathways analogous to that known in other
pro- and eukaryotic models have been described also in organs and cells
of a few mono- and dicotyledonous plant species . They include an excision
DNA repair after the action of alkylating agents and UV light, repair of
ionizing radiation-induced DNA single strand breaks and bleomycin-induced
double strand breaks as well as recovery of short daughter DNA strands
synthesized on templates damaged by alkylating agents . Several DNA-glycosylases,
UV- and AP-endonucleases have been isolated and the role of DNApolymerases
and DNA-ligases in the repair processes in plants has been
investigated . Special topics in plants rpresent the repair of spontaneous
DNA lesions accumulated in seeds during their ageing, repair capacity of
pollen grains and chloroplasts and the clastogenic adaptation - an analogy
of adaptive response at the chromosome level . At the absence of repair
deficient mutants in plants, metabolic inhibitors and artificial conditions
like storage of mutagen-treated seeds help to elucidate the role
of repair pathways in the mutagenic efficiency . A new approach in determining
the involvement of individual DNA lesions in the mutagenic processes
in plants represents the transfer of an E .coli repair gene ada into
tobacco that enhances resistance of Jobacco oe s against the a-cTion of
alkylating agents interacting with 0 in DNA guanine .
THE ROLE OF TRANSCRIPTION IN UV-INDUCED EXCISION REPAIR
J . Venema, L .H .F . Mullendere, A . van Hoffen and A .A . van Zealand . Department of
Radiation Genetics and Chemical Mutagenesis . State University of Leiden, The
Netherlands .
Preferential repair of active genes following exposure to UV-light (254 nm) is now
a well established feature of mamaulian cells . We have shown that in normal human
fibroblasts the transcriptionally active adenosine d .aminase (ADA) gene is faster and
more efficiently repaired than the genoma overall . The inactive 754 locus is repaired
to the saao extent as the genome overall .
We have extended these studies by assessing the role of transcription in excision
repair . First, we have analyzed repair in the ADA gene with strand specific probes . We
show that in a fragment comprising the 3' end of the gene there is no difference in
repair of both strands . A second approach was made by using a cell strain derived from
a patient with severe combined immunodeficiency (SCID) which is homozygous for a
deletion in the promoter region of the ADA gene . In primary fibroblasts no transcription
of the ADA gene is detectable by Northern blotting' . Our results show that repair in
two adjacent fragments of the ADA gane is similar to that in normal human cells . We are
currently investigating strand specificity of repair in this cell strain .
1 . Berkvens, Th .M . et al . (1987), Nucl . Acids Res . 15, 9365-9378 .
OVERVIEW OF BACTERIAL TE8TIN0 FOR MUTA08NICITY
S. VenNt, Institute of Csncsr Research: Royal Marsdsn Hosplul, 8udton, Sumy SM2 IfNO, United Kkqdom
604
605
it Is dlHlcuM, N not Imposslble to say anything about bsdsrld gsnotoxdolty tats which has not bsw
sak( already. The discovery of oncogsns activation by point mutation (a:9., bass-pak substitution) has phrsn
a naw leass of life to bacterial mulagsnetiol.b. Point mutations are paRbulsrly easy to detact in the
S.Imonslla/mkxosoms assay, which Is by far the most widely used mutation assay aver dsvbsd . A search on
ToxNne using -Ames" as the key word resulted In 7,'00 oBatloia In February 1ssY. The Ama test has bssn Ln
subjected to criticism (both Informed and uninformsd), natimwl and International ragdstlon (blind, or not 0
bland), with easy, difficult or knpossibls chemksis . lt has nsisbd this global bsttsrkp with remarkable polas, Co
and Is more or tas unchanged from the form 11 took In the wJd4wvonfts when M Mt emerged . Despite ths O%
appearance of a vaMty of alternative tests (aE ., nvans•nwlatbn In straba of EsohMdda ood WP2; t0
fluctuation tes(s ; forward mutation assays; methods, suoh as ths 808 CfKOmotsst, which employ Induction
of the 808 DNA-prooastrp network as s signal of DNA danrgr dllbrsnllsl taodoKy In npat profbisnt and J
N
N