[Studies of the repair of radiation-induced genetic damage in Drosophila]. Annual progress report, June 1, 1989--September 1, 1990 Page: 1 of 7
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Annual Progress Report
for the period FA /5 ~ t. J 5
June 1, 1989 to September 1, 1990 / o 3 7
1. Overview. The most exciting discovery we have made over the past year derives
from an analysis of the interaction between DNA repair and P-element transposition. In
that study Dr. Banga has developed a powerful new system for analyzing the repair of
DNA double-strand breaks. We have also completed a screen of mutagenized autosomes
obtained from two San Francisco laboratories with the recovery of several mutants-that will
provide the foundation for future efforts to clone repair related genes. At the same time,
strong progress has been made in the cloning and characterization of the repair-related
genes mei-41 and mus209. Finally, our efforts to clone the mei-9 gene have uncovered the
existence of a unsuspected feature of the system used for transposon-tagging in
Drosophila. This new knowledge will aid our future cloning efforts as well as those of
others in the field.
2. Cloning of repair genes by transposon tagging. During the previous year,
Mrs. Rosenstein, together with others in the laboratory, had completed a screen of 2600
stocks obtained from UC San Francisco for transposon insertions in repair-related genes.
Since transposon tagging is rapidly becoming the method of choice for cloning Drosophila
genes, she spent much of the current year screening an additional 3,000 stocks from the
Rubin lab at Berkeley. Several promising mutants have been recovered from that screen as
well. This collection of repair-deficient mutations with potential transposon insertions
promises to accelerate the recovery of additional repair-related genes.
3. Transposition as a tool to study the repair of double-strand DNA breaks.
At this time last year we had obtained preliminary evidence suggesting that the mei41 gene
is required for the recovery of chromosomes undergoing P transposition. Since then that
conclusion has been strongly substantiated and, together with the Engels laboratory, we
have further documented that the repair mechanism which is defective in mei-41 involves
gene conversion. Since the intermediate in that repair process is, in all likelihood, a DNA
double-strand break, P transposition can provide a precise means to study the repair of
DNA double-strand breaks in a site specific manner. A systematic screen of other
Drosophila mus mutations has revealed that the mus302 gene is also required in this repair
pathway. This study has, therefore, identified two Drosophila genes that participate in the
repair of one class of DNA double-strand breaks. In addition, it has established P
transposition as a valuable tool for investigating the mechanism of that process.
4. Characterization of the mei-41 gene. Having cloned the mei-41 gene in a -
chromosomal walk, we are now in the process of identifying a transcription unit and a
coding sequence. This has not turned out to be a trivial task because, as we knew from
previous genetic studies, this is a relatively large gene for this organism. Accordingly we
have initiated a program to subclone the entire mei-41 region into plasmid vectors to
facilitate the transcription analysis. In proceeding bidirectionally from the P insertion sites,
which define essential mei-41 sequences, we have thus far identified two transcription units
and a possible third one. This time last year we believed that the transcription unit to the
left of the P insertions on the clone map was related to mei-41. Since several tests of that
hypothesis have failed to confirm that conclusion, it now seems possible that that gene is
nested in an intron within the mei-41 gene. David Binninger has recently used Northern
blotting to identify alternate transcribed sequences which show strong promise of being
derived from the mei-41 gene.
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[Studies of the repair of radiation-induced genetic damage in Drosophila]. Annual progress report, June 1, 1989--September 1, 1990, report, December 31, 1990; Davis, California. (https://digital.library.unt.edu/ark:/67531/metadc702135/m1/1/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.