Table 1.

IFN-ω in different species and the characteristics of the IFN-ω gene and protein.

Species	Location	Characteristics of the IFN-ω gene and protein	Reference
Human	Human chromosome 9	Human IFN-ω has at least five members, but only one member of the human IFN-ω family is a functional gene that results in a functional and glycosylated protein. This protein has six additional amino acids located at its carboxyl-terminus (172 amino acid residues) and a single polypeptide chain comprising two disulfide bonds and an N-glycosylation-linked site at amino acid 80. In terms of the primary structures of the type I IFNs, there is approximately 75% amino acid sequence identity between IFN-α and IFN-ω.	[8], [9], [12], [15], [23]
Cat	No data	Felines IFN-ω (FeIFN-ω) includes 13 subtypes that contain an amino-terminal secretory signal sequence from residues 1–23. The mature sequence of IFN-ω contains four highly conserved cysteines (positions 1, 29, 100, and 140) and seven prolines (four of those at positions 4, 26, 39, and 117 of the mature protein), while the FeIFN-ω protein has six additional amino acids at its carboxyl-terminus compared with FeIFN-α. Among these subtypes, FeIFN-ω2 and FeIFN-ω4 contain a seven-amino-acid insertion at position 109, and the insert location is comparable to that of the FeIFN-α, while it has higher antiviral activity than the other subtypes. Interestingly, different from that in other mammalian subtypes, these 13 subtypes do not have an N-glycosylation recognition site.	[16], [24]
Pig	Chromosome 1	Porcine IFN-ω (PoIFN-ω) contains seven or eight members with variable open reading frame lengths. The most extensive similarity of the PoIFN-ω sequences are to bovine leukocyte IFN-ω, and the lowest one is to equine IFN-ω. It contains an IFabd functional domain, multiple putative binding sites for type I IFN receptor subunits, and one putative N-glycosylation site (Asn/Asp-X-Ser/Thr). The subtypes of the IFN-ω protein, which have five alpha-helices, bear amino-terminal 20- to 30-amino-acid signal peptides and four conserved cysteine residues, Cys24, Cys52, Cys122, and Cys162, which are also found in IFN-α1. In addition, all IFN-ω subtypes, except IFN-ω1 (whose carboxyl-terminus is 11 residues shorter than the other PoIFN-ω subtypes), have 14 or 16 extended residues, while the pairs IFN-ω2/6 and IFN-ω3/5 share identical sequences.	[17], [25], [26]
Horse	Chromosome 23	Horse IFN-ω contains eight members plus four pseudogenes, which is a greater than the number of IFN-α genes and more diverse than the other type I IFN genes. The IFN-ω gene contains a putative glycosylation sequence, Asn-Thr-Thr, at positions 78–80. The IFN-ω protein has six alpha-helices and it contains IFabd (cd00095), interferon (pfam00143), and IFabd (smart00076) domains, and multiple putative binding sites for the type I IFN receptor subunit 1 and 2 and an N-glycosylation site. Notably, the length of the open reading frame of each IFN-ω subtype is invariant.	[18], [27]
Rabbit	No data	The rabbit IFN-ω family comprises at least eight genes that display the highest degree of homology with human IFN-ω and the lowest with murine IFN-αII. There are two IRF-1 binding sites at nucleotide positions 85 and 55, the hexamer repeat sequence 5′–GAAANN–3′ in the 5′ noncoding sequence, and a repetition of the 5′–TTATTTAT–3′ motif, which is similar to many 3′ downstream regions of genes encoding inflammatory cytokines. In addition, the immediate promoter region of the rabbit IFN-ω genes has a high proportion of purine residues. An ATG sequence, (5′–GAAATG–3′), was found only in the promoter region of RbIFNW48 at nucleotide position 66. Similarly, IFN-ω includes four Cys residues at amino acid positions 1, 29, 99, and 139.	[19]
Cattle	Chromosome 8q15	The IFN-ω family in cattle (BoIFN-ω) consists of 24 members that contain two pseudogenes and 22 functional genes. Among these subtypes, the nucleotide similarity is 91.3%–97.2%, and the amino acid identity is 84.4%–95.4%. Most of these subtypes encode 195 amino acids, expect BoIFN-ω7 and BoIFN-ω11, which lack nine amino acid residues at their carboxyl terminus. In addition, 23 of the members have signal peptides. A glycosylation site analysis revealed that BoIFN-ω 1, 2, 3, 4, 7, 9, 10, 11, 12, 13, 17, 20, 23 and 24 do not have a N-glycosylation site, while BoIFN-ω 1, 2, 3, 7, 13, 17, 20, 23, and 24 have one O-glycosylation site; BoIFN-ω 4 and 10 have three O-glycosylation sites, and BoIFN-ω 9,11, and 12 have two O-glycosylation sites. There are four conserved cysteines at positions 1, 29, 99, and 139, and one conserved arginine at position 161 in the mature peptide sequences; the cysteines at positions 1 and 29, and 99 and 139 positions could form two disulfide bonds. The three-dimensional structure of BoIFN-ω3 includes five alpha-helices.	[21], [28], [29], [30], [31]
Serotine bat	No data	The serotine bat IFN-ω genes are intronless, and its open reading frame consists of 588 bp (encoding 195 amino acids), and N-glycosylation sites were identified. Transcription factor binding sites, such as IRFs, ISREs, ATF2/c-Jun, and NF-κB, were found in the promoter region sequences at bp 1071. The potential transcription start sites of the genes are located at bp 1071 of the esIFN-ω promoter sequences.	[20]
Sheep	No data	Sheep IFN-ω concludes as least five members. All the putative IFN regulatory motifs found in the BoIFN-ω gene promoter are also conserved in the promoter region of the sheep gene, such as the three 5′–GAAANN–3′ motifs (− 51 to − 46, − 57 to − 52, and − 67 to − 62), which overlap two potential interferon regulatory factor-1 binding sites “8” (5′–AAATGA–3′, positions − 55 to − 50 and − 66 to − 61), and a fourth 5′–GAAANN–3′ hexamer (− 97 to − 92) which overlaps a third less conserved interferon regulatory factor-1 site in the sheep clone (5′–AACTGA–3′, positions − 101 to − 96).	[22], [32]