Worm Breeder's Gazette 11(5): 20

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.

The Cloning of a Putative C. elegans Cyclin B Gene Using the Polymerase Chain Reaction

James Richards, Joseph Temenak and Karen Bennett

Figure 1

Cyclin proteins are intimately involved in cell cycle regulation.  
Two types of cyclin proteins have been identified, cyclin A and cyclin 
B.  The cyclin A protein has been shown to be critical to embryonic 
development in Drosophila; homozygous mutant embryos lacking cyclin A 
die when zygotic transcription fails to provide cyclin A.  The 
presence of cyclin B protein cannot rescue these mutants (C.F.  Lehner 
and P.H.  O'Farrell, Cell 1990.  61:535-547).  No mutants in cyclin B 
have been reported in Drosophila.  Cyclin B protein has been shown to 
be involved in meiotic maturation in clams (Westendorf et al., J.  
Cell Biol.  1989.  108:1431-1444).  Perhaps surprisingly, in 
Drosophila the mRNA for cyclin B localizes by in situ hybridization to 
the Drosophila pole cells, the fly equivalents of the nematode P 
germline cell lineage (Whitfield et al., Nature 1989.  338:337340).
The Bennett laboratory is interested in the nematode germline 
lineage and in identifying the components of the germline P granules (
Strome and Wood, Cell 1983.  35:15-25 and K.  Bennett, WBG 9:1 55).  
We plan to determine if nematode cyclin B RNA is similarly localized 
to the nematode germline precursor cells, and would like to address 
what possible role the sequestration of cyclin B RNA plays in the 
determination of the germline.  
Using primers to conserved cyclin B regions, we have isolated, 
cloned and sequenced a PCR product from genomic Caenorhabditis DNA 
which is a putative cyclin B.  As illustrated below, this fragment has 
72% exact match at the amino acid level to the corresponding region of 
the clam or sea urchin cyclin B genes; this is exactly the same match (
41/57 aa) that sea urchin and clam show to each other in this region.  
Southern blot analysis using this fragment as a probe with C.  elegans 
DNA indicates a single copy gene.  The PCR fragment recognizes a 
single 1.4 kb message on Northern analysis using polyA+ RNA from mixed 
stage worms; this size is large enough to accommodate the coding 
region of the cyclin B protein.  We have recently screened R.  
Barstead's lambda ZAP mixed stage cDNA library.  Thirty putative 
cyclin B cDNAs were detected on duplicate lifts when 120,000 phage 
were screened.
[See Figure 1]

Figure 1