Calmodulin gene expression during sea urchin development: persistence of a prevalent maternal protein
Abstract
Calmodulin gene expression during embryogenesis of the sea urchin Strongylocentrotus purpuratus was investigated. Several identical bacteriophages containing a cDNA insert encoding sea urchin calmodulin (CM-1) were identified by screening a lambda gt10 library of S. purpuratus gastrula-stage cDNAs with a chicken calmodulin cDNA sequence. A 1.2-kb cDNA fragment from CM-1 was subcloned into pUC-8 to give plasmid pCAL-8. pCAL-8 contains a single open reading frame encoding 79 amino acids, a termination codon, and 0.9 kb of 3'-untranslated message. This sea urchin amino acid sequence shows 95% homology to amino acid residues 69-148 of the predicted sequence of chicken calmodulin. Northern analysis showed that pCAL-8 hybridizes to a single size (3.2 kb) of mRNA in both embryonic and adult somatic tissues. Genome blots suggested that there is a single calmodulin gene in the S. purpuratus genome. We used pCAL-8 to study calmodulin mRNA accumulation in S. purpuratus embryos. Calmodulin mRNA is present in the unfertilized egg at the level of a typical rare-class mRNA (1000-2000 transcripts) and accumulates approximately 100-fold to levels representing about 1/10th of 1% of the total mRNA in pluteus-stage cells. Synthesis of calmodulin, ...Continue Reading
References
Patterns and rates of protein synthesis in sea urchin embryos. II. The calculation of absolute rates
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