Alternative titles; symbols
HGNC Approved Gene Symbol: ILF3
Cytogenetic location: 19p13.2 Genomic coordinates (GRCh38) : 19:10,654,346-10,692,400 (from NCBI)
For background information, see NF45 (ILF2; 603181).
Kao et al. (1994) cloned cDNAs encoding NF45 and NF90. The NF90 gene encodes a 671-amino acid polypeptide with limited similarity to several RNA-binding proteins. The NF90 gene also appears to encode an alternatively spliced 404-amino acid polypeptide, of which the first 394 amino acids are identical to the longer clone. Northern and Western blot analysis demonstrated NF45 and NF90 expression in several cell types, including both unstimulated and stimulated Jurkat T cells.
By immunoscreening a HeLa cell cDNA library for phosphoproteins, Matsumoto-Taniura et al. (1996) isolated a partial cDNA encoding ILF3, which they termed MPP4. Immunoprecipitation analysis indicated that MPP4 encodes 90- and 110-kD proteins. Immunofluorescence microscopy demonstrated cytoplasmic expression during M phase and nuclear/nucleolar expression during interphase.
Patel et al. (1999) purified double-stranded RNA (dsRNA)-binding proteins from HeLa cell extracts and microsequenced a 90-kD protein with identity to MPP4 in its N terminus. Using a yeast 2-hybrid screen with a mutant RNA-activated protein kinase (PRKR; 176871) as bait, followed by RT-PCR, they isolated a full-length cDNA encoding ILF3, which they called DRBP76. Sequence analysis predicted that the 702-amino acid protein has a bipartite nuclear localization signal, 2 dsRNA-binding domains, an RG2 domain, and multiple potential phosphorylation sites. SDS-PAGE analysis showed expression of a 90-kD protein, larger than the calculated 76 kD. EMSA analysis confirmed the dsRNA binding activity of DRBP76. Autoradiographic analysis indicated that DRBP76 is phosphorylated by PRKR.
Langland et al. (1999) noted that NF90 is primarily localized to ribosomes.
Saunders et al. (2001) obtained a cDNA encoding DRBP76, which they termed NFAR1, as well as a variant cDNA encoding a 110-kD, 894-amino acid protein they designated NFAR2. Sequence analysis showed that the NFAR proteins share homology with a known PRKR substrate, the translation initiation factor EIF2S1 (603907). Northern blot analysis revealed ubiquitous expression of multiple transcripts ranging from 4.0 to 8.0 kb. Immunoblot analysis indicated variable expression with lower amounts particularly notable in liver and spleen, suggesting differential regulation at the translational or posttranslational level. Immunoblot analysis and confocal microscopy demonstrated that PRKR and both NFAR variants reciprocally coimmunoprecipitate and colocalize in the nucleus. Immunoprecipitation analysis indicated an association with spliceosomes.
Viranaicken et al. (2006) identified splice variants of human and mouse ILF3 that encode long and short isoforms of the ILF3 and NF90 proteins via inclusion or exclusion of 13 N-terminal residues, respectively.
Kao et al. (1994) showed that the NF45 and NF90 proteins form an NFAT DNA-binding activity that is enhanced by T-cell stimulation and inhibited by cyclosporin A and FK506.
Functional analysis by Saunders et al. (2001) indicated that both NFAR proteins regulate gene transcription, probably at the level of mRNA elongation. NFAR2 exhibited potent, constitutive regulatory activity through its unique C-terminal region, which specifically interacted with FUS (137070) and SMN1 (600354). Saunders et al. (2001) concluded that NFARs facilitate dsRNA-regulated gene expression at the level of posttranscription.
Shim et al. (2002) showed that NF90 binds to a subregion of the 3-prime untranslated region that contains several AU-rich elements (AREs) and slows down the degradation of IL2 (147680) mRNA. In nonstimulated cells, NF90 was mostly nuclear, but T-cell activation resulted in its accumulation in the cytoplasm. The authors concluded that nuclear export of NF90 is required for IL2 mRNA stabilization.
Pfeifer et al. (2008) found that NFAR1 and NFAR2 were involved in retaining cellular transcripts in intranuclear foci and could regulate mRNA export to the cytoplasm. They also remained associated with exported ribonucleoprotein complexes. Treatment of HeLa cells with small interfering RNA to NFAR1 and/or NFAR2 resulted in an increase in protein synthesis rates, particularly in the presence the mRNA export factors TAP (NXF1; 602647), p15 (NXT1; 605811), or RAE1 (603343). Depletion of NFAR in mouse fibroblasts or HeLa cells dramatically increased their susceptibility to vesicular stomatitis virus or influenza virus, respectively. Pfeifer et al. (2008) concluded that NFAR1 and NFAR2 are retained on polyribosomes and act to govern translation rates, and that they also play a role in innate immune defense to virus infection.
By genomic sequence analysis, Saunders et al. (2001) determined that the NFAR gene contains 21 exons and spans 16.2 kb. The 90-kD NFAR1 variant expresses exon 18, which contains several stop codons that lead to termination at amino acid 702. The 110-kD NFAR2 variant lacks exon 18 but contains exons 19, 20, and 21.
Viranaicken et al. (2006) identified an additional alternatively spliced exon within intron 2 of the mouse and human ILF3 genes, increasing the total number of exons to 22.
Saunders et al. (2001) mapped the NFAR gene to chromosome 19p13 by FISH.
Pfeifer et al. (2008) found that mice lacking Nfar died in utero.
Kao, P. N., Chen, L., Brock, G., Ng, J., Kenny, J., Smith, A. J., Corthesy, B. Cloning and expression of cyclosporin A- and FK506-sensitive nuclear factor of activated T-cells: NF45 and NF90. J. Biol. Chem. 269: 20691-20699, 1994. [PubMed: 7519613]
Langland, J. O., Kao, P. N., Jacobs, B. L. Nuclear factor-90 of activated T-cells: a double-stranded RNA-binding protein and substrate for the double-stranded RNA-dependent protein kinase, PKR. Biochemistry 38: 6361-6368, 1999. [PubMed: 10320367] [Full Text: https://doi.org/10.1021/bi982410u]
Matsumoto-Taniura, N., Pirollet, F., Monroe, R., Gerace, L., Westendorf, J. M. Identification of novel M phase phosphoproteins by expression cloning. Molec. Biol. Cell 7: 1455-1469, 1996. [PubMed: 8885239] [Full Text: https://doi.org/10.1091/mbc.7.9.1455]
Patel, R. C., Vestal, D. J., Xu, Z., Bandyopadhyay, S., Guo, W., Erme, S. M., Williams, B. R. G., Sen, G. C. DRBP76, a double-stranded RNA-binding nuclear protein, is phosphorylated by the interferon-induced protein kinase, PKR. J. Biol. Chem. 274: 20432-20437, 1999. [PubMed: 10400669] [Full Text: https://doi.org/10.1074/jbc.274.29.20432]
Pfeifer, I., Elsby, R., Fernandez, M., Faria, P. A., Nussenzveig, D. R., Lossos, I. S., Fontoura, B. M. A., Martin, W. D., Barber, G. N. NFAR-1 and -2 modulate translation and are required for efficient host defense. Proc. Nat. Acad. Sci. 105: 4173-4178, 2008. [PubMed: 18337511] [Full Text: https://doi.org/10.1073/pnas.0711222105]
Saunders, L. R., Jurecic, V., Barber, G. N. The 90- and 110-kDa human NFAR proteins are translated from two differentially spliced mRNAs encoded on chromosome 19p13. Genomics 71: 256-259, 2001. [PubMed: 11161820] [Full Text: https://doi.org/10.1006/geno.2000.6423]
Saunders, L. R., Perkins, D. J., Balachandran, S., Michaels, R., Ford, R., Mayeda, A., Barber, G. N. Characterization of two evolutionarily conserved, alternatively spliced nuclear phosphoproteins, NFAR-1 and -2, that function in mRNA processing and interact with the double-stranded RNA-dependent protein kinase, PKR. J. Biol. Chem. 276: 32300-32312, 2001. [PubMed: 11438536] [Full Text: https://doi.org/10.1074/jbc.M104207200]
Shim, J., Lim, H., Yates, J. R., III, Karin, M. Nuclear export of NF90 is required for interleukin-2 mRNA stabilization. Molec. Cell 10: 1331-1344, 2002. [PubMed: 12504009] [Full Text: https://doi.org/10.1016/s1097-2765(02)00730-x]
Viranaicken, W., Gasmi, L., Chauvin, C., Denoulet, P., Larcher, J.-C. Identification of a newly spliced exon in the mouse Ilf3 gene generating two long and short isoforms of Ilf3 and NF90. Genomics 88: 622-632, 2006. [PubMed: 16952437] [Full Text: https://doi.org/10.1016/j.ygeno.2006.08.006]