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Comments on Momoyo Hanazawa et al. (2003) International Worm Meeting "A C. elegans homologue of eukaryotic initiation factor 5A, IFF-1, is required for germ cell proliferation, gametogenesis and P-granule localization of PGL-1" (0)
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Momoyo Hanazawa, Ichiro Kawasaki, Hirofumi Kunitomo, Keiko Gengyo-Ando, Karen L Bennett, Shohei MItani, & Yuichi Iino (2003). A C. elegans homologue of eukaryotic initiation factor 5A, IFF-1, is required for germ cell proliferation, gametogenesis and P-granule localization of PGL-1 presented in International Worm Meeting. Unpublished information; cite only with author permission.
Eukaryotic initiation factor 5A (eIF-5A) was originally identified as a protein that stimulates translation. However, recent studies have suggested its involvement in regulation of mRNA stability and nucleo-cytoplasmic shuttling of mRNA. TheC. elegans genome contains two genes, iff-1 and iff-2, encoding homologues of eIF-5A. Deletion mutants of iff-1, iff-1(tm483), show sterility, with small gonads, while deletion mutants of iff-2, iff-2(tm393), show slow larval growth and abnormalities in somatic gonadal structures. iff-1 is expressed only in gonads, while iff-2 is somatically expressed. We further examined the cause of the sterility in the iff-1 mutants. In the wild type, the number of germ nuclei increases slowly up to the L3 stage and thereafter increases dramatically. In the iff-1 mutant, the slow increase continues into adulthood, leading to a small number of germ cells (about 20 per gonad arm). Treatment of the gld-2(q497); gld-1(q485) tumorous germline mutant with the iff-1 dsRNA results in few germ nuclei like the iff-1 mutant, indicating that iff-1 is required for proliferation of germ cells. However, staining for phosphorylated histone H3, an M phase marker, shows that germ cells are not arrested at a specific stage of the cell cycle. Staining the mutant with an HIM-3 antibody indicates meiotic germ nuclei are present, but mature gametes are never observed. The iff-1 phenotype is reminiscent of losses of the P-granule components PGL-1 or GLH1/4. P granules localize near nuclear pores in the gonads. We found localization of the P-granule component PGL-1 to nuclear pores disrupted in the iff-1 mutant, with GLH-1 and GLH-4 unaffected. Yeast two hybrid analysis suggests the possibility that IFF-1 physically interacts with PGL-1. In light of the proposed roles for P granules in post-transcriptional regulation of gene expression, these results suggest a possibility that IFF-1 interacts with P granules and participates in the regulation of mRNA metabolism on P granules.