Worm Breeder's Gazette 9(3): 67

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5S DNA Transcription in vitro

D.W. Nelson and B.M. Honda

Figure 1

Cell free extracts of C. support RNA pol 
III specific transcription of circular plasmid templates carrying C. 
sequences encoding 5S or tRNAs. We are 
engaged in the identification of template sequences required for 
efficient 5S rRNA transcription in vitro.
We have constructed a set of 5' and 3' deletion derivatives of a 
transcriptionally active C. DNA repeat. The 
efficiency of 5S rRNA transcription from these mutant templates was 
determined relative to a tRNA internal control template provided by R. 
Devlin and M. Khosla. The results show that template sequences 
immediately 5' to the 5S rRNA coding region are required for efficient 
transcription in vitro.
The C. briggsae genome contains two distinct 5S DNA repeat families (
1.0 and 0.7 kb HindIII fragments) which are organized in mutually 
exclusive tandem clusters. The 1 kb 5S DNA repeat is efficiently 
transcribed in the C.  while the 0.7 kb 5S 
DNA repeat appears to be transcriptionally inactive. These results 
suggest that C. briggsae may differentially express these two 5S DNA 
repeat families.
The relative efficiency of 5S rRNA transcription from the wild-type 
C. briggsae 1 kb 5S DNA repeat and its 5' deletion derivatives in the C. 
confirms the requirement for 5' flanking 
sequences noted above. Comparison of C. 
riggsae sequences flanking the 5S rRNA coding 
sequence carried by the 1 kb 55 DNA repeats reveals the presence of a 
13 bp conserved sequence. Deletions affecting the integrity of this 
putative regulatory element are transcribed at approximately 1/10 the 
wild type level. The figure below shows the location of this element 
and the position and transcriptional efficiency of deletion templates 
affecting this region.

Figure 1