Worm Breeder's Gazette 14(2): 74 (February 1, 1996)

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.

Protein kinase C isoforms in Caenorhabditis elegans

Yo Tabuse, Toshie Miyamoto, Johji Miwa

NEC Fundamental Research Laboratories, Tsukuba, Ibaraki 305, Japan

Protein kinase C is thought to play pivotal roles in various cellular
signaling pathways. More than ten isoforms have been identified from
mammalian species to form a PKC family having similar structures and
functions. From C. elegans, three PKC isoforms were so far reported, one
of them being the gene tpa-1, which is, amongst others, most similar to
PKCdelta/theta of a novel PKC type(1). The tpa-1 gene mediates the action
of tumor-promoting phorbol esters to cause behavioral abnormality and
developmental arrest. Although loss-of-function mutaions in tpa-1 confer
resistance to phobol esters on C. elegans(2), mutants do not show
phenotypes detectably different from the wild type in the absence of
phorbol esters. This observation has led us to suppose that some other
isoform(s) with lower sensitivity to phorbol compounds operates in the
tpa-1 signaling pathway. To understand more about the tpa-1 pathway, as
well as those other pathways mediated by other PKC isoforms, it is
necessary to identify and analyze other PKCs.
Several cDNA clones presumptive for encoding PKCs have been 
identified by Y. Kohara et al. in their cDNA sequencing project: they 
are yk4h6, yk17b2, yk45d8, yk17b9, and yk5d4. As we reported at the 
last C. elegans meeting, we started to analyze these clones. Sequencing 
the clone yk4h6 and its extended 5' region, which was obtained by 5' 
RACE, we  found that it is a derivative from a message homologous to 
PKCzeta as implied by its overall similarity to human PKCzeta of 55%. 
It was mapped onto chromosome II, and the genomic region that covers 
the clone was sequenced by the C. elegans Genome Consortium. Comparison 
of our cDNA sequence with the sequence data from the Consortium showed 
that the gene consists of nine exons and contains those exon/intron 
boundaries as exactly predicted by Genefinder. A trans-spliced leader 
sequence different from either SL1 and SL2 was found on the the 5' end 
of the message. 
The cDNA clones of both yk17b2 and yk45d8 were originally indicated 
by Y. Kohara et al. to encode PKCmu homolog. Since yk17b2 contains a 
short insert, we screened and sequenced a longer clone from Barstead's 
cDNA library. Although a partial sequence of the  clone proved to be 
similar to that of PKCmu, it turned out to be different from that of 
yk45d8. So, C. elegans seems to possess at least two PKCmu isoforms. 
Partial sequences of the clones yk17b9 and yk5d4 revealed that they are 
similar to the amino-terminal half and the carboxy-terminal half of the 
tpa-1 product, respectively. These clones, however, each detected mRNA 
of different sizes, thus indicating different genic origins of these 
We plan to analyze the expression patterns of genes for these 
clones with lacZ or GFP gene fusion and to find out their functions 
with antisense RNA expression. 

(1) T. Sano et al.  J. Mol. Biol. (1995) 251, 477-485.
(2) Y. Tabuse et al.  Biochem. J. (1995) 312, 69-74.