Abstract
RIO protein kinases (RIOKs) are a relatively conserved family of enzymes implicated in cell cycle control and ribosomal RNA processing. Despite their functional importance, they remain a poorly understood group of kinases in multicellular organisms. Here, we show that the C. elegans genome contains one member of each of the three RIOK sub-families and that each of the genes coding for them has a unique tissue expression pattern. Our analysis showed that the gene encoding RIOK-1 (riok-1) was broadly and strongly expressed. Interestingly, the intestinal expression of riok-1 was dependent upon two putative binding sites for the oxidative and xenobiotic stress response transcription factor SKN-1. RNA interference (RNAi)-mediated knock down of riok-1 resulted in germline defects, including defects in germ line stem cell proliferation, oocyte maturation and the production of endomitotic oocytes. Taken together, our findings indicate new functions for RIOK-1 in post mitotic tissues and in reproduction.
Highlights
Protein kinases form a large family of diverse regulatory enzymes that are encoded by approximately two percent of the genes in most metazoan genomes [1, 2]
RIO protein kinases (RIOKs)-2 kinases are most similar in the amino terminal half of the protein where two domains are identified: the RIOK-2 Nterminal domain which is similar to winged helix domains and may be able to bind DNA [10] and the RIOK-1 catalytic domain
We showed that the C. elegans genome encodes three members of the RIOK family, and that RIOK-1 and-2 are essential for larval development
Summary
Protein kinases form a large family of diverse regulatory enzymes that are encoded by approximately two percent of the genes in most metazoan genomes [1, 2]. Of the 518 protein kinases encoded in the human genome, 478 form a single superfamily known as the eukaryotic protein kinase (ePK) family [1]. These enzymes are defined by their conserved, bi-lobed catalytic core which contains 12 subdomains involved in substrate binding, ATP binding and catalysis [3]. A second, smaller superfamily of 40 ‘atypical’ protein kinases (aPK) share structural homology to the ePK catalytic core, but lack overall sequence similarity [4]. The aPKs are divided into 13 small homology groups, one of which is the right open reading frame (RIO) family of kinases
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