Analysis of Micronuclear, Macronuclear and cDNA Sequences Encoding the Regulatory Subunit of cAMP-Dependent Protein Kinase of Euplotes octocarinatus: Evidence for a Ribosomal Frameshift

Abstract We have isolated and characterized the micronuclear gene encoding the regulatory subunit of cAMP-dependent protein kinase of the ciliated protozoan Euplotes octocarinatus, as well as its macronuclear version and the corresponding cDNA. Analyses of the sequences revealed that the micronuclear gene contains one small 69-bp internal eliminated sequence (IES) that is removed during macronuclear development. The IES is located in the 5′-noncoding region of the micronuclear gene and is flanked by a pair of tetra-nucleotide 5′-TACA-3′ direct repeats. The macronuclear DNA molecule carrying this gene is approximately 1400 bp long and is amplified to about 2000 copies per macronucleus. Sequence analysis suggests that the expression of this gene requires a +1 ribosomal frameshift. The deduced protein shares 31% identity with the cAMP-dependent protein kinase type I regulatory subunit of Homo sapiens, and 53% identity with the regulatory subunit R44 of one of the two cAMP-dependent protein kinases of Paramec...