Worm Breeder's Gazette 16(2): 38

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

C. elegans RAD51 promoter is activated after gamma-irradiation 

Cinzia Rinaldo1, Paolo Bazzicalupo1, Sara Ederle2, Massimo Hilliard1, Adriana La Volpe1

1 International Institute of genetics and Biophysics -CNR - 10, Via Marconi 80125 Naples Italy 
2 Dipartimento di Genetica e Biologia Generale e Molecolare, Facolta' di Scienze, Universita' di Napoli "Federico II"- 8, Via Mezzocannone 80134 Naples, Italy 

Eukaryotic genes, defective in the repair of DNA damage, were isolated in yeast and shown to be involved both meiotic recombination and recombinatorial repair of double strand breaks (DSBs) on DNA. They belong to the RAD52 homologous recombination pathway. The Rad51 protein in particular is structurally and functionally related to the RecA gene product of Escherichia coli. It catalizes strand transfer between homologous DNA molecules, mutations in this gene lead to enhanced sensitivity to genotoxic agents (like X- and gamma-radiation that induce DSBs), reduction of mitotic recombination and impaired meiosis.
We have cloned the RAD51 homolog in C. elegans  (Rinaldo et al. 1998) . Using a CeRAD51 promoter fusion with the reporter gene LacZ in Andy Fire's  vector pPD96.04, we have been observed, that the C. elegans RAD51 promoter is activated after gamma-irradiation.
The construct was injected in lin-15 adult hermaphrodites using the lin-15 wild type gene as transformation marker. We obtained 5 independent transformed lines. The expression pattern observed was consistent in the different lines: about 30 % of lin-15+ animal express the reporter LacZ gene in a limited number of cells varying in quantity and type between different animals and stages.
A population of transgenic hermaphrodite worms was syncronized and samples at different stages were subjected to gamma-irradiations (12000 rad with a Cs137 source). The treatment results in an overall enhancement in the expression of the reporter gene, LacZ, driven by the CeRAD51 promoter, and in an increse in the number of animals expressing the transgene in the population. Statistical analysis based on the number of worms expressing LacZ before and after induction is summarized in the following table.

 
control
control
control
gamma-treated
gamma-treated
gamma-treated
 
 
Stage
LacZ
tot
%
LacZ
tot
%
c2
P
L1
9
120
7.5
17
110
15
3.6
0.075
L2
12
100
12
40
200
20
3.2
0.08
L3/L4
18
145
12
61
131
42
39
<0.0001
L4/ y. a.
22
110
20
65
130
50
23
<0.0001
adults
14
55
25
53
67
79
35
<0.0001
dauer
24
108
22
67
158
42
11.5
0.0007
tot
99
638
15
303
796
38
88
<0.0001

Rinaldo C., Ederle S., Rocco V., and Volpe A. L. (1998) The Caenorhabditis elegans RAD51 homolog is transcribed into two alternative mRNAs potentially encoding proteins of different sizes.  Mol. Gen. Genet. 260 : 289-294.