Worm Breeder's Gazette 10(2): 113
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.
In the last WBG, we reported on the identification of the 2.4kb HindIII fragment as a part of the tpa-1 gene and on the isolation of cDNA clones from a cDNA library (kindly provided by Drs. J. Kimble and J. Ahringer) that have homology to the 2.4kb fragment. One of the positive clones contained a 1.8kb insert. Sequencing of this insert, designated cDNA#1, dictated a part of a putative open reading frame with the stop codon TGA at position 1581 that can encode a protein of 526 amino acids. We think that the 5' region of the mRNA corresponding to cDNA#1 extends beyond the 5' region of this cDNA as there is no translation starting codon at this end. A database search using the amino acid sequence deduced from cDNA#1 revealed that the conceptual tpa-1 protein is highly homologous to protein kinase C's ( PKC) of various animals including man. PKC's are a family of multiple types with similar structures composed of an amino-terminal regulatory domain and carboxyl-terminal kinase domain. Each domain possesses two evolutionarily conserved regions. As shown below, the amino acid sequence from aa1 to aa150 of the tpa-1 protein is significantly homologous to the amino terminal region of all known PKC's. About 45% of the amino acids in this conserved region are identical to those of other animal PKC's. A twice tandemly repeated cysteine-rich sequence of the motif, C-X(2)-C-X(13)-CX(2)-C-X(7)-C-X(7)-C, which characterizes all known PKC's, is also present in this region. The region of aa151 to 230 bears no homology to any region of PKC. The tpa-1 protein lacks a sequence corresponding to one of the conserved region, termed C2, found in the regulatory domain of all the reported PKC's. The amino acid sequence from aa231 to aa526 exhibits substantial homology to the kinase domain of various other protein kinases, such as A-kinase (40% identical) and G kinase (40%). But, as shown below, it shares the highest homology to PKC's(55 to 60%). Taking into account conservative amino acid replacement, the homology to the known PKC kinase domain reaches higher than 80%. To summarize the results obtained so far, a PKC-like protein encoded by the tpa-1 gene is involved in the action of tumor promoting phorbol esters(TPPE) and plays a crucial role in the behavior and the development of C. elegans. Work is now underway to analyze mutant alleles induced by both EMS mutagenesis and Tc1 insertion to gain an insight into the interaction between the tpa-1 protein and TPPE and into a mechanism of turning the gene resistant to TPPE. [See Figures 1-2]