Structure and developmental expression of Strongyloides stercoralis fktf-1, a proposed ortholog of daf-16 in Caenorhabditis elegans.
A forkhead transcription factor gene, fktf-1, which we propose to be orthologous to the Caenorhabditis elegans dauer-regulatory gene daf-16 has been discovered in the parasitic nematode Strongyloides stercoralis. Genomic and cDNA sequences from both species predict alternately spliced a and b message isoforms. In contrast to C. elegans, where two a isoforms, daf-16a1 and daf-16a2, are found, a single fktf-1a isoform is found in S. stercoralis. Five of the 10 introns found in the C. elegans gene are found in the proposed S. stercoralis ortholog. Functional motifs common to DAF-16 and several mammalian forkhead transcription factors are conserved in FKTF-1. These include the forkhead DNA binding domain, four Akt/protein kinase B phosphorylation sites and a C-terminal domain that may associate with factors such as the steroid receptor coactivator and other factors necessary for transcriptional regulation. An N-terminal serine-rich domain found in DAF-16A is greatly expanded in FKTF-1A. This domain is missing in DAF-16B, FKTF-1B and all mammalian orthologs. FKTF-1 shows the closest phylogenetic relationship to DAF-16 among all known mammalian and nematode forkhead transcription factors. Like its proposed Caenorhabditis ortholog, the fktf-1 message is expressed at all stages of the life cycle examined thus far. Discovery of fktf-1 indicates the presence of an insulin-like signalling pathway in S. stercoralis similar to that known to regulate dauer development in C. elegans. This pathway is a likely candidate to control infective larval arrest and reactivation as well as regulation of the switch between parasitic and free-living development in the parasite.
Massey
Holman C
HC
Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104-6050, USA. hmassey@vet.upenn.edu
Nishi
Manami
M
Chaudhary
Kshitiz
K
Pakpour
Nazzy
N
Lok
James B
JB
D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics; D029742:Caenorhabditis elegans Proteins; D051858:Forkhead Transcription Factors; D015870:Gene Expression; D017238:Genes, Helminth; D006801:Humans; D007814:Larva; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000032:analysis; D016415:Sequence Alignment; D017385:Sequence Homology; D017171:Strongyloides stercoralis / Q000235:genetics* / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics*
D029742:Caenorhabditis elegans Proteins; D051858:Forkhead Transcription Factors; D012333:RNA, Messenger; D014157:Transcription Factors; C108831:daf-16 protein, C elegans