Worm Breeder's Gazette 13(2): 56 (February 1, 1994)
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.
Actins are well conserved proteins, showing at least 75% identity in primary sequence between species as divergent as animals, plants, and unicellular organisms. In contrast, recently discovered actin-related proteins demonstrate 35 to 55% identity to conventional actins. At least three different classes of actin-related proteins have been identified; proteins within one class are significantly more similar to each other than to actin or actin-related proteins in another class. To date, three different actin-related proteins have been discovered in C. elegans: arp-1 , arp-2 ,and arp-3 (for actin related proteins-1, 2, and 3) fall in the three distinct classes, showing ~50%, ~47%, and ~33% identity to actins respectively. These genes were first identified in random cDNA tagging projects (1,2); cDNA sequences were subsequently determined (3).
arp-1 ,shows ~50% homology to C. elegans actins, but is even more similar to human Act-RPV protein (67%). Act-RPV is an integral component of the multi-protein dynactin complex, an activator of cytoplasmic dynein based vesicle transport. Although the C. elegans dynactin complex has not been isolated, homologs of two dynactin complex components, the actin-capping proteins subunits Cap-1 and Cap-2 ,have been identified and characterized (4, 5). Antibodies to C. elegans actin-capping protein recognize transient structures in early C. elegans embryos. The pattern of transient structures suggests a role for actin-capping protein in rotation of the mitotic spindle in the P1 lineage (5, 6, 7). The actin-capping protein in the transient structures may function as a component of a dynactin complex (5). This would suggest co-localization of actin-capping protein and other components of dynactin complex, including that of actin-related protein.
We are interested in testing the predicted localization and function of the actin-related protein encoded by arp-1 .To initiate the analysis of arp-1 ,we have mapped the gene to right end of chromosome II, right of unc-52 .PCR assays specific to arp-1 position the gene near the right ends of the YACs Y53F4 and Y106A11 .In addition, we find that the arp-1 probe weakly hybridizes to a distinct sequence located on a free contig located near the right end of chromosome III. We have narrowed the location to a region common to YACs Y37D8 , Y39E4 , Y106H1 ,and Y107A12 .The location of this sequence is close to but distinct from that of act-5 (see abstract by Schriefer et al) which also maps to the YAC Y107A12 .We plan to clone both the arp-1 gene on chromosome II, and the homologous sequence from chromosome III. Interestingly, probes corresponding to the two actin-related genes arp-2 ,and arp-3 each also identify two distinct genomic locations, suggesting that C. elegans may contain as many as six arp genes. We plan to (i) examine the expression patterns of arp-1 and related genes using in-situ hybridizations and/or specific antibodies and (ii) isolate mutations in the gene(s) and examine the effect of the mutation(s) on development of the animal.
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