Programmed Translational Frameshifting Is Likely Required for Expressions of Genes Encoding Putative Nuclear Protein Kinases of the Ciliate Euplotes octocarinatus

Abstract Three macronuclear genes encoding putative nuclear protein kinases of the ciliate Euplotes octocarinatus syngen 1 were isolated and sequenced. All three deduced gene products share significant properties with a group of recently identified nuclear serine/threonine protein kinases named Ndr. The three predicted proteins contain the twelve conserved catalytic subdomains of protein kinases and 22 near universally-conserved amino acids residues that are characteristic of serine/threonine protein kinases. In addition, there is an ∼30 amino acid-peptide insertion between subdomains VII and VIII that contains a potential nuclear localization signal. Sequence analysis suggests that expression of the Eondr2 gene requires a +1 programmed translational frameshift for its translation. Comparison of the deduced EoNdr2 with other known Ndr protein kinases implies that a +1 ribosomal frameshift occurs at the motif AAATAA.