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Annual report : National Institute of Environmental Health Sciences (Volume 1981) online

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approval, the data is stored in readily accessable tables for future
reference and summary management tables are updated with the new information,
Data from other test systems is being entered into PROPHET by NIEHS
personnel .

Analytical techniques required to perform mutagenicity and quality control
determinations are being developed by EMTDP scientists for addition by
BBN into PROPHET. Finally, BBN is currently working on new interactive
and batch report generation routines to facilitate the management of the
EMTDP results.

SIGNIFICANCE TO BIOMEDICAL RESEARCH AND THE PROGRAM OF THE INSTITUTE :
This system will allow the timely and accurate collection and retrieval
of laboratory test data, and will also provide EMTDP management with a
tool to manage the results, produce management reports and provide analyses
to back-up mutagenicity determinations. It is the first system of its
type to provide all of these facilities in such a fashion for use by non-
computer-oriented management personnel.



440



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PROJECT NUMBER (Oo NOT use this space)



U.S. DEPARTMENT OF

HEALTH AND HUMAN SERVICES

PUBLIC HEALTH SERVICE

NOTICE OF

INTRAMURAL RESEARCH PROJECT



PROJECT NUMBER



ZOl ES 60102-03 LMG



PERIOD COVERED

October 1. 1980 to September 30, 1981



TITLE OF PROJECT (80 characters or less)

Testing of Chemicals of Interest in Salmonella



NAMES, LABORATORY AND INSTITUTE AFFILIATIONS, AND TITLES OF PRINCIPAL INVESTIGATORS AND ALL OTHER
PROFESSIONAL PERSONNEL ENGAGED ON THE PROJECT

PI: E. Zeiger Supervisory Microbiologist LMG NIEHS
D. Pagano Research Microbiologist LMG NIEHS



COOPERATING UNITS (if any)



LAB/BRANCH

Laboratory of Molecular Genetics



SECTION



INSTITUTE AND LOCATION

NIEHS, NIH, Research Triangle Park, North Carolina 27709



TOTAL MANYEARS:
0.4



PROFESSIONAL!

0.1



0.3



CHECK APPROPRIATE BOX(ES)
□ (a) HUMAN SUBJECTS

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D (b) HUMAN TISSUES



XS (c) NEITHER



SUMMARY OF WORK (200 words or less - underline keywords)

Salmonella typhimurium strains TA98, TAIOO, TA1535, TA1537 and TA1538
are being used to test chemicals of interest for mutagenicity . A series
of cyclic hydrazides which are analogs of nitrosamines have been tested
for mutagenicity for comparison with mutagenic and non-mutagenic
nitrosamine counterparts. In addition Dimethyl ami noazobenzene (Butter
yellow) and two of its analogues, as well as 2,3,7,8-Tetrachloredi-
benzofuran and alkyl nitrites will be tested.



441



PHS-6040
(Rev. 2-81)



ZOl ES 60102-03 LMG



PROJECT DESCRIPTION

METHODS EMPLOYED : The standard Salmonella plate test procedure of Ames
with some modification or liquid suspension tests were used.

MAJOR FINDINGS AND PROPOSED COURSE : All hydrazides were mutagenic for
TA-1535 and TA-lOO in the absence of S9. No activity was seen against
TA-98 either with or without S-9. TA-1535, in all cases, showed a con-
sistently higher response than TA-100. The mutagenicity results obtained
with these hydrazides have been compared with mutagenicity results
obtained with the corresponding nitrosamines and no quantitative correlations
have been noted.

2,3,7,8-Tetrachlorodibenzofuran (TCDF) and the alkyl nitrites are
currently being tested. Butter yellow and its two analogues are all
mutagenic for TA1538, but have differing activities. In order to
obtain the optimum mutagenic activity, increased levels of S-9 were
needed. The Salmonella results obtained with butter yellow and its
analogues will be compared with results obtained in other microbial and
whole animal systems.

SIGNIFICANCE TO BIOMEDICAL RESEARCH AND THE PROGRAM OF THE INSTITUTE :
Cyclic hydrazides are used as organic intermediates in organic synthesis
reactions. This demonstration of their mutagenicity has implications
for the health of workers handling these chemicals. It does not appear
as if these hydrazides are the active metabolites of nitrosamines but
they are potentially hazardous in their own right. TCDF and alkyl
nitrites are substances to which the population is exposed. Examination
of their mutagenicity will provide information that can be used in risk
estimation procedures, should they become necessary.

Butter yellow and its analogues will provide structure/activity information
that may be useful in predicting the toxicity of other, related substances.

PUBLICATIONS

Zeiger, E. and J. Guthrie (1981). Cyclic hydrazides are mutagenic for
Salmonella typhimurium. Mutation Res. (in press).



442



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PROJECT NUMBER (Oo NOT use this space)



U.S. DEPARTMENT OF

HEALTH AND HUMAN SERVICES

PUBLIC HEALTH SERVICE

NOTICE OF

INTRAMURAL RESEARCH PROJECT



PROJECT NUMBER



ZOl ES 60105-03 LMG



PERIOD COVERED

October 1. 1980 to September 30, 1981



TITLE OF PROJECT (80 characters or less)

Genetic Control of Mutation



NAMES, LABORATORY AND INSTITUTE AFFILIATIONS, AND TITLES OF PRINCIPAL INVESTIGATORS AND ALL OTHER
PROFESSIONAL PERSONNEL ENGAGED ON THE PROJECT



PI



J. M. Mason



Geneticist



LMG



NIEHS



COOPERATING UNITS (if any)

B. Slatko, Department of Biology, Williams College, Williamstown, MA



lab/branch
Laboratory of Molecular Genetics



INSTITUTE AND LOCATION

NIEHS, NIH, Research Triangle Park, North Carolina



27709



TOTAL MANYEARS:
1.9



PROFESSIONAL:
0.4



OTHER:



1.5



CHECK APPROPRIATE BOX(ES)
D (a) HUMAN SUBJECTS

D (al) MINORS n (a2) INTERVIEWS



n (b) HUMAN TISSUES



(c) NEITHER



SUMMARY OF WORK (200 words or less - underline keywords)

It has become evident in the last several years that mutation rate is
under genetic control. In bacteria and yeast the frequency of induced
mutations can be either increased or decreased by blocking one or another
pathway of DNA repair . This project is designed to determine the relation-
ship betv^een DNA repair and mutagenesis in Drosophila melanogaster . Tv^o
approaches are being taken: (1) A mutant which increases the mutation
frequency (a mutator ) has been identified and is being characterized; and
(2) The interaction of DNA repair defective mutants and hybrid dysgenesis
(naturally occurring mutators) is being observed in double mutant com-
binations.



443



PHS-6040
(Rev. 2-81)



ZOl ES 60105-03 LMG



PROJECT DESCRIPTION

METHODS EMPLOYED : Standard genetic manipulations utilizing well-
characterized mutants and chromosomal aberrations in Drosophila
melanogaster are employed.

MAJOR FINDINGS AND PROPOSED COURSE : One mutator being examined is
unable to repair X-ray induced breaks in the normal way. In the
presence of the mutator broken chromosomes are recovered which appear
to be deficient for a telomere [on both cytological and genetic grounds].
That is, unlike X-ray induced aberrations in wild type, the broken
chromosomes do not appear to be capped by any previously existing telo-
mere. The mutator is recessive, and maps to chromosome III. It is
active throughout oocyte development, but does not appear to be active
during spermiogenesis. The mutator does not increase the frequency of
meiotic nondisjunction. It does, however, increase the frequency of X-
chromosome loss. These losses are the results of whole arm deletions
in which the centromere is recovered but the rest of the X has been lost.

Certain naturally occurring mutators ("hybrid dysgenic strains") have
very specific phenotypes in terms of where in the genome they allow
mutation, chromosome breakage or recombination to occur. It has been
hypothesized that the genetic changes induced in the presence of hybrid
dysgenesis are the result of DNA sequences inserting into or excising
from genomic DNA. If this is the case the cell's DNA repair capacity
may play a role in movement of these sequences. We are making com-
binations of DNA repair deficient mutants and hybrid dysgenic factors
to look for quantitative changes in mutation, recombination and seg-
regation. The most striking observation so far is that the recovery
of the dysgenic factor from a hybrid male decreases fromn,aboutr0.4
in the controls to almost zero in the presence of mei-41 or
This is true for three independent dysgenic factors.

SIGNIFICANCE TO BIOMEDICAL RESEARCH AND THE PROGRAM OF THE INSTITUTE :
This study will lead to an understanding of the cellular mechanisms
used to regulate the rates of mutation and chromosome breakage. It
should in the long run allow one to sequence a telomere.

PUBLICATIONS

Mason, J.M.: Spontaneous mutation frequencies in mutagen-sensitive
mutants of Drosophila melanogaster . Mutation Res. 72: 323-326, 1980.



444



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PROJECT NUMBER (Do NOT use this space)



U.S. DEPARTMENT OF
\ HEALTH AND HUMAN SERVICES
PUBLIC HEALTH SERVICE
NOTICE OF
INTRAMURAL RESEARCH PROJECT



PROJECT NUMBER



ZOl ES 60106-03 LMG



PERIOD COVERED

October 1, 1980 to September 30, 1981



TITLE OF PROJECT (80 characters or less)

Cytogenetic Analysis of Mutagen-Sensitive Mutants



NAMES, LABORATORY AND INSTITUTE AFFILIATIONS, AND TITLES OF PRINCIPAL INVESTIGATORS AND ALL OTHER
PROFESSIONAL PERSONNEL ENGAGED ON THE PROJECT

PI: J.M. Mason Geneticist LMG NIEHS
N.N. Scobie Visiting Fellow LMG NIEHS



COOPERATING UNITS (if any)

J.B. Boyd, Department of Genetics, University of California, Davis, CA



lab/branch
Laboratory of Molecular Genetics



INSTITUTE AND LOCATION

NIEHS, NIH, Research Triangle Park, North Carolina 27709



TOTAL MANYEARSi
1.2



PROFESSIONAL:
1.1



OTHER:



0.1



CHECK APPROPRIATE BOX(ES)
Q (a) HUMAN SUBJECTS

□ (al) MINORS a (a2) INTERVIEWS



n (b) HUMAN TISSUES



)P((c) NEITHER



SUMMARY OF WORK (200 words or less - underline keywords)

Mutagen-sensitive mutants defective in DNA repair mechanisms are collected
in Drosophila melanogaster . The mutants are characterized cytogenetically
in order to gain a basic understanding of the genetic control of sensitivity
to mutagenic agents . The tests used in the initial characterization of
these mutants include genetic and cytogenetic mapping, complementation
analysis, tests for sensitivity to unrelated mutagens, and tests for
pleio-tropic effects on related functions such as recombination . At the
present time a fine structure map of the mei-41 region is being constructed
in order to ascertain the all el ism relationship of mus 104 and mei-41 as
vi/ell as to confirm the large size of mei 41 found during mutational
analysis.



445



:K. PI

k



PHS-6040
(Rev. 2-81)



ZOl ES 60106-03 LMG



PROJECT DESCRIPTION



METHODS EMPLOYED : Standard genetic manipulations utilizing well -char-
acterized _X-1 inked mutants and chromosomal aberrations in Drosophila
melanogaster are employed. Because the mutagen-sensitive (mus ) mutifnts
are X^-1 inked the presence of these mutants is monitored by mating mus
males to attached-X^ females, treating the progeny with MMS (or other
mutagen), and checking the sex ratio of the survivors.

MAJOR FINDINGS AND PROPOSED COURSE : Mutants in two putative mus^ loci
are '^ery similar in phenotype in that they are sensitive to the same
mutagens and they are defective in post-replication repair. However,
post-replication repair in mutants at one "locus" (mus 104) is sensitive
to caffeine while post-replication repair in mutants at the other (mei-
41) is not. It is not clear from the initial mapping nor from comple-
mentation studies whether these mutants are allelic. A fine structure
map is being constructed to clarify the allelic relationship of these
mutants. The results so far lead to the following conclusions, (a).
Two mus 104 alleles map within the mei-41 locus and thus are allelic,
(b). If mus 104 and mei-41 are allelic they cannot define two different
genes or two different pathways of post-replication repair as proposed
by Boyd et al . (c). Since mei-41 and mus 104 have different effects
on meiosis but the same effect on sensitivity to mutagens it is possible
to uncouple the effects of mutants of this locus in different tissues.
The reason for this uncoupling may become evident after other alleles
are added to the map of this region, (d). The mei 41 locus is ^ery
large in recombinational terms (0.25 centimorgani]"!^ It is the largest
locus known in Drosophila and 50 X the size of a simple gene such as
ry_. This is consistent with the observation that mei 41 is about 25
X the size of a typical mus X-1 inked gene in a mutational study. Making
the usual assumptions as to the genome size and the amount of recom-
bination in Drosophila we calculate that the mei 41 locus contains
about 145 kb and that if a protein product is made it should be about
5 X 106 daltons.

SIGNIFICANCE TO BIOMEDICAL RESEARCH AND THE PROGRAM OF THE INSTITUTE :
An understanding of the action of genes controlling mutagen sensitivity
is necessary for understanding DNA repair, mutagenesis, recombination
and chromosome stability.

PUBLICATIONS

Mason, J. M., Green, M.M., Shaw, K.E.S., and Boyd, J.B.: Genetic analysis
of X-linked mutagen-sensitive mutants of Drosophila melanogaster .
Mutation Res. (in press).



446



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PROJECT NUMBER (Do NOT use this space)



U.S. DEPARTMENT OF

HEALTH AND HUMAN SERVICES

PUBLIC HEALTH SERVICE

NOTICE OF

INTRAHURAL RESEARCH PROJECT



PROJECT NUMBER



ZOl ES 60107-03 LMG



PERIOD COVERED

October 1, 1980 to September 30, 1981



TITLE OF PROJECT (80 characters or less)



Molecular Cloning and Sequence Analysis of Various Regions of the T4 Genome

NAMES, LABORATORY AND INSTITUTE AFFILIATIONS, AND TITLES OF PRINCIPAL INVESTIGATORS AND ALL OTHER
PROFESSIONAL PERSONNEL ENGAGED ON THE PROJECT



PI:
Other:



A. Sugino

M. A. Conkling



Visiting Scientist
Geneticist



LMG
LMG



NIEHS
NIEHS



COOPERATING UNITS (if any)



None



lab/branch

Laboratory of Molecular Genetics



SECTION



INSTITUTE AND LOCATION

NIEHS. NIH. Research Triangle Park. North Carolina 27709



TOTAL MANYEARS:



0.3



PROFESSIONAL:



0.2



0.1



CHECK APPROPRIATE BOX(ES)
D (a) HUMAN SUBJECTS

D (al) MINORS n (a2) INTERVIEWS



□ (b) HUMAN TISSUES



CX(c) NEITHER



I



SUMMARY OF WORK (200 words or less - underline keywords)

The bacteriophage T4 is a powerful tool in the analysis of basic mechanisms of
mutagenesis. The genetics of the rll region have been extensively used and
inferences of particular mutagenic pathways can be made. With molecular
clonging and DNA sequencing techniques we can now confirm certain inferred
pathways. Cloned sequences will also aid in the biochemical analysis of certain
T4 functions involved in fidelity and repair. The genome of bacteriophage T4
will be cloned by recombinant DNA techniques. The primary cloning vector will
be M13. The cloned sequences will be pooled and probed for various regions of
interest either by DNA: DNA hydridization or by their ability to complement or
recombine with T4 phage defective for the desired activity. These regions will
then be sequenced or used in biochemical analyses.



447



PHS-6040
(Rev. 2-81)



Z01 ES 60107-03 LMG

PROJECT DESCRIPTION

METHODS EMPLOYED : Purified T4 DNA will be digested with restriction endonuclease
Tag I. Vector Ml 3 mp7 replicative form DNA is restricted by restriction
endonuclease Ace I and the generated ends are filled with dTTP. Both DNAs are
annealed, ligated by DNA ligase and transformed by E. coli . Clones of interest
will be selected by hybridization, complementation or marker rescue. Identified
cloned DNA will be sequenced by Sanger's dideoxynucleotides termination methods.

MAJOR FINDINGS AND PROPOSED COURSE : We have been trying to sequence regions of
the T4 rll genes without first cloning them. This approach uses an end-labeled
restriction fragment of part of the rll gene. This fragment is annealed to the
separated T4 DNA strands and act as a primer for DNA sequence method. However,
T4 DNA is too long and causes high backgrounding. Meanwhile, it is discovered
that restriction endonuclease TaqI can digest T4 DNA, unlike other restriction
endonucleases. We are now developing a technique to clone Taql-digested T4 DNA
into a Ml 3 vector.

SIGNIFICANCE TO BIOMEDICAL RESEARCH AND THE PROGRAM OF THE INSTITUTE : Much of
what we know of basic mechanisms of mutagenesis has been inferred from the
genetic system of phage T4. The cloning and sequencing of certain mutants will
allow us to verify proposed pathways of mutagenesis by environmental mutagens.



448



SMITHSONIAN SCIENCE INFORMATION EXCHANGE
PROJECT NUMBER (Do NOT use this space)



U.S. DEPARTMENT OF

HEALTH AND HUMAN SERVICES

PUBLIC HEALTH SERVICE

NOTICE OF

INTRAMURAL RESEARCH PROJECT



PROJECT NUMBER



ZOl ES 60108-03 LMG



PERIOD COVERED

October 1. 1980 to September 30, 1981



TITLE OF PROJECT (80 characters or less)



Mechanism of DNA Replication in Prokaryotes



NAMES, LABORATORY AND INSTITUTE AFFILIATIONS, AND TITLES OF PRINCIPAL INVESTIGATORS AND ALL OTHER
PROFESSIONAL PERSONNEL ENGAGED ON THE PROJECT



PI: A. Sugino

Other: K. C. Kim

J. Arendes

P. Carl



Visiting Scientist
Visiting Fellov/
Visiting Fellovi/
Guest Worker



LMG NIEHS

LRDT & LMG NIEHS

LMG NIEHS

LMG NIEHS



COOPERATING UNITS (if any)

Dept. of Biophysics & Theoretical Biology, Univ. of Chicago, Chicago, IL
Dept. of Pharmacology, Univ. of North Carolina, Chapel Hill, NC



lab/branch

laboratory of Molecular Genetics



INSTITUTE AND LOCATION

NTFHS, NTH, Research Triangle Park. North Carolina 27709



total MANYEARS:



2JL



PROFESSIONAL:



2JL



CHECK APPROPRIATE BOX(ES)
□ (a) HUMAN SUBJECTS

D (al) MINORS n (a2) INTERVIEWS



□ (b) HUMAN TISSUES



[^ (c) NEITHER



SUMMARY OF WORK (200 words or less - underline keywords)

A) An in vitro replication system for bacteriophage N4 has been developed to
study the mechanism of its DNA replication . The system mimics in vivo DNA
replication. The DNA replication proceeds continuously from both ends of the
DNA molecule as in vivo . By using this system, we have purified three DNA
replication proteins to homogeneity and identified their functions.

B) The Guest Worker (P. Carl) has isolated a mutant which is deficient in
RNaseH activity. It has been speculated that RNaseH removes RNA primer from
"Okazaki Fragment". We have studied the RNaseH mutant genetically and
biochemically. Also, we have been cloning the RNaseH gene to generate a
much tighter mutant of RNaseH by in vitro mutagenesis .



449



PHS-6040
(Rev. 2-81)



ZOl ES 60108-03 LMG



PROJECT DESCRIPTION

METHODS EMPLOYED : In vitro DNA synthesis system. Wild type and various DNA
replication-negative N4 phages and the crude extracts from those phage-infected
cells. Conventional column chromatographies and velocity sedimentation for
purification of DNA replication proteins. Standard cloning technique. Restriction
endonucleases. DNA-DNA and colony hybridization. RNaseH assay using RNA-DNA
hybrid. Electron microscope, agarose and polyacrylamide electrophoresis, and
electrofocusing gel.

f^AJOR FINDINGS AND PROPOSED COURSE : A) N4 DNA replication. Col i phage N4 contains
a linear double stranded DNA genome of 72 kb pairs and a DNA dependent RNA poly-
merase in its virions. N4 DNA replication does not require the activity of E.
coli genes dnaA , dnaB , dnaC , dnaE , dnaG and polA . Mutants in at least eight N4
cistrons affect N4 DNA replication. One cistron codes for the virion RNA poly-
merase required for the synthesis of N4 early RNAs. The products of three other
cistrons are required for transcription of N4 middle RNAs which code for at least
four functions involved in DNA synthesis (DO). Moreover, a study of the behavior
of temperature sensitive mutants in the virion RNA polymerase suggest that it also
plays a direct role in N4 DNA replication. We have developed an in vitro system
to study the mode of initiation of N4 DNA replication. N4 infected cells are
gently lysed and the soluble proteins are concentrated by ammonium sulphate
precipitation. DNA synthesis in this extract is totally dependent on the addition
of exogenous native N4 DNA. N4 heat denatured and other DNAs are poor templates.
No activity is detected in extracts derived from N4 DO mutant infection. However,
mixing of extracts from two DO mutants, in different cistrons, restores activity
to nearly wild type levels. We are using this complementation assay to purify
the N4 coded components required for in vitro DNA synthesis. In the course of
these experiments, the cistrons corresponding to the N4 coded DNA polymerase and
DNA-binding protein have been identified and purified to homogeniety. In vitro
N4 DNA replication starts from both ends of the DNA molecule and proceeds
continuously as does in vivo . B) £. coli RNaseH. 1) The E. coli rnh gene will
be cloned in order to confirm the map location we have assigned to this gene.
Such a clone will probably be an overproducer of this important enzyme. 2) Using
the cloned DNA and in vitro mutagenesis techniques we will construct potential
RNase H mutants which will be propagated on plasmids. By inducing recombination
between host and plasmid rnh sequences we plan to produce strains carrying solely
mutant rn]i sequences. Alternatively RNase mutants will be selected by classical
in vivo techniques of localized mutagenesis. 3) The rnh mutants will be
characterized with respect to their growth and macromolecular synthesis. In
particular we shall examine DNA synthesis in the mutants to see if we can find
evidence for an increased number of Okazaki pieces bearing RNA primers or changes
in the length of primers. 4) The new rnh alleles will be combined with mutants
such as polAexl already known to affect the processing of Okazaki pieces to see
if more severe defects in the processing are found in the double mutant.

SIGNIFICANCE TO BIOMEDICAL RESEARCH AND THE PROGRAM OF THE INSTITUTE : These
studies help to understand the complexity of DNA replication, particularly the
importance of replication protein complex, and will provide a precise understanding
of mutagenic mechanisms.



450



ZOl ES 60108-03 LMG



PUBLICATIONS

Sugino, A., Higgins, N. P., and Cozzarelli, N. R.: Covalent attachment of
the DNA gyrase A protein to DNA. Nucleic Acids Res . 8, 3865-3874 (1980).

ABSTRACTS

Risk, J. K. , Sugino, A., and Rothman-Denes, L. B,: In vitro coliphage N4 DNA
replication. ICN-UCLA Symposia, Molecular and Cellular Biology - Structure and
DNA-Protein Interactions of Replication Origins. J^. Supramol . Structure , Supl.
5, p. 340 (1981).

Sugino, A., Risk, J. K. and Rothman-Denes, L. B.: In vitro coliphage N4 DNA
replication: Purification of N4 DNA replication proteins. Cold Spring Ha:"bor
Phage meeting (1981 ).



V

I



451



SMITHSONIAN SCIENCE INFORMATION EXCHANGE
PROJECT NUMBER (Do NOT use this space)



U.S. DEPARTMENT OF

HEALTH AND HUMAN SERVICES

PUBLIC HEALTH SERVICE

NOTICE OF

INTRAMURAL RESEARCH PROJECT



PROJECT NUMBER



Z01 ES 60109-03 LMG



PERIOD COVERED



October 1. 1980 to September. 30. 1981



TITLE OF PROJECT (80 characters or less)



Mprhaniqm nf HNA rppliratinn in Pii kflrynt.PS



NAMES, LABORATORY AND INSTITUTE AFFILIATIONS, AND TITLES OF PRINCIPAL INVESTIGATORS AND ALL OTHER
PROFESSIONAL PERSONNEL ENGAGED ON THE PROJECT



PI: A. Sugino

Other: H. Kojo

J. Arendes

K. C. Kim

B. D. Greenberg



Visiting Scientist
Guest Worker
Visiting Fellow
Visiting Fellow
Biologist



LMG


NIEHS


LMG


NIEHS


LMG


NIEHS


LMG


NIEHS


LMG


NIEHS



COOPERATING UNITS (if any)



Noa



LAB/BRANCH



I flhnrat.nry nf Mnlpcular Genptic;



INSTITUTE AND LOCATION

NTFHS. NTH, Rp^Parrh Triannip Park, North r.a



rnlina ?77nq



TOTAL MANYEARS:



-2.i.



PROFESSIONAL:



CHECK APPROPRIATE BOX(ES)
D (a) HUMAN SUBJECTS

D (al) MINORS n (a2) INTERVIEWS



J-JEl



OTHER:



D (b) HUMAN TISSUES



(c) NEITHER



SUMMARY OF WORK (200 words or less - underline keywords)

A) The Drosophila mutant which possesses an altered DNA polymerase a has been
further characterized. Similar types of DNA polymerase mutants have been
isolated from the yeast Saccharomyces cerevisiae and it has been proven that
DNA polymerase I is a true DNA replicase in yeast.

B) An in vitro DNA replication system of yeast 2 ym plasmid has been developed
from a crude extract of S^. cerevisiae . The in vitro origin and direction of
plasmid 2 pm DNA replication have been determined and are the same as in vivo



C) In order to understand the importance of DNA tertiary cf^nr-f-nrp -Por qma
replication, DNA topoisomerases, which might play an important '"ole in DNA



Online LibraryNational Institute of Environmental Health ScienceAnnual report : National Institute of Environmental Health Sciences (Volume 1981) → online text (page 38 of 92)