Exploring features and function of Ss-riok-3, an enigmatic kinase gene from Strongyloides stercoralis

Abstract

Background: Right open reading frame protein kinase 3 (RIOK-3) belongs to the atypical kinase family. Unlike th other two members, RIOK-1 and RIOK-2, which are conserved from Archaea to humans, RIOK-3 occurs only i multicellular organisms. Studies on HeLa cells indicate that human RIOK-3 is a component of the 40S small ribosom subunit and supports cancer cell growth and survival. However, almost nothing is known about the function of RIOK-3 We explored the functional role of RIOK-3 encoding gene from Strongyloides stercoralis, a parasitic nematode of human and dogs Methods: To analyze the gene and promoter structure of Ss-riok-3, RACE-PCR and Genome-walker PCR were performe to isolate the full length cDNA, gDNA and promoter region of Ss-riok-3. RNA-seq was conducted to assess the transcrip abundance of Ss-riok-3 in different stages of S. stercoralis. Transgenesis was employed to determine the anatomi expression patterns of Ss-riok-3 Results: The RIOK-3 protein-encoding gene (designated Ss-riok-3) of S. stercoralis was characterized. The full-lengt complementary and genomic DNAs of the RIOK-3 encoding gene (riok-3) were isolated from this nematode. The cDN of Ss-riok-3 is 1,757 bp in length, including a 23 bp 5'-UTR, a 36 bp 3'-UTR and a 1,698 bp coding region encoding protein of 565 amino acids (aa) containing a RIO kinase domain. RNA sequencing (RNA-seq) analysis revealed tha Ss-riok-3 is transcribed in all developmental stages of S. stercoralis assessed, with transcripts being particularly abundan in parasitic females. Gene structure analysis revealed that Ss-riok-3 contains no intron. The putative promoter contain conserved promoter elements, including four TATA, two GATA, one inverse GATA and one inverse CAAT boxes. Th promoter of Ss-riok-3 drives GFP expression in the head neuron, intestine and body wall muscle of transgeni S. stercoralis larvae, and the TATA boxes present in the 3'-UTR of the gene immediately upstream of Ss-riok-3 initiat transcription Conclusions: The characterization of the RIOK-3 encoding gene from S. stercoralis provides a sound foundation fo investigating in detail its function in the development and reproduction of this important pathogen.