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Structural and functional characterization of salmon STAT1, STAT2 and IRF9 homologs sheds light on interferon signaling in teleosts.

Sobhkhez M, Skjesol A, Thomassen E, Tollersrud LG, Iliev DB, Sun B, Robertsen B, Jørgensen JB - FEBS Open Bio (2014)

Bottom Line: Overexpression of STAT2a or STAT2b together with STAT1a activated a GAS-containing reporter gene construct in IFNγ-stimulated cells.The highest induction of GAS promoter activation was found in IFNγ-stimulated cells transfected with IRF9 alone.Taken together, these data suggest that salmon STAT2 and IRF9 may have a role in IFNγ-induced signaling and promote the expression of GAS-driven genes in bony fish.

View Article: PubMed Central - PubMed

Affiliation: The Norwegian College of Fishery Science, UiT The Arctic University of Norway, N-9037 Tromsø, Norway.

ABSTRACT
Mammalian IRF9 and STAT2, together with STAT1, form the ISGF3 transcription factor complex, which is critical for type I interferon (IFN)-induced signaling, while IFNγ stimulation is mediated by homodimeric STAT1 protein. Teleost fish are known to possess most JAK and STAT family members, however, description of their functional activity in lower vertebrates is still scarce. In the present study we have identified two different STAT2 homologs and one IRF9 homolog from Atlantic salmon (Salmo salar). Both proteins have domain-like structures with functional motifs that are similar to higher vertebrates, suggesting that they are orthologs to mammalian STAT2 and IRF9. The two identified salmon STAT2s, named STAT2a and STAT2b, showed high sequence identity but were divergent in their transactivation domain (TAD). Like STAT1, ectopically expressed STAT2a and b were shown to be tyrosine phosphorylated by type I IFNs and, interestingly, also by IFNγ. Microscopy analyses demonstrated that STAT2 co-localized with STAT1a in the cytoplasm of unstimulated cells, while IFNa1 and IFNγ stimulation seemed to favor their nuclear localization. Overexpression of STAT2a or STAT2b together with STAT1a activated a GAS-containing reporter gene construct in IFNγ-stimulated cells. The highest induction of GAS promoter activation was found in IFNγ-stimulated cells transfected with IRF9 alone. Taken together, these data suggest that salmon STAT2 and IRF9 may have a role in IFNγ-induced signaling and promote the expression of GAS-driven genes in bony fish. Since mammalian STAT2 is primarily an ISGF3 component and not involved in IFNγ signaling, our finding features a novel role for STAT2 in fish.

No MeSH data available.


Related in: MedlinePlus

Relative gene expression of STAT2a/b and IRF9 in tissues from healthy Atlantic salmon The relative expression of STAT2a/b (A) and IRF9 (B) in the tissues heart, gill, intestine, spleen, posterior kidney (P. Kidney), head kidney (H. K), liver, skin, thymus and muscle were measured by qPCR and presented relative to EFlαβ by the formula (ctEFlαβ)/(ct of STAT2 or IRF9) Samples from 6 fish were analyzed and error bars represents the mean ±SD.
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f0015: Relative gene expression of STAT2a/b and IRF9 in tissues from healthy Atlantic salmon The relative expression of STAT2a/b (A) and IRF9 (B) in the tissues heart, gill, intestine, spleen, posterior kidney (P. Kidney), head kidney (H. K), liver, skin, thymus and muscle were measured by qPCR and presented relative to EFlαβ by the formula (ctEFlαβ)/(ct of STAT2 or IRF9) Samples from 6 fish were analyzed and error bars represents the mean ±SD.

Mentions: Tissues taken from healthy Atlantic salmon (heart, gill, intestine, spleen, posterior kidney (P. Kidney), head kidney (HK), liver, skin, thymus and muscle) were analyzed by qPCR using primer pairs detecting both STAT2a/b isoforms and IRF9 (Table 1). Results showed that STAT2a/b and IRF9 were expressed in all tissues tested. STAT2a/b revealed the highest relative expression in heart, gill, intestine, HK, muscle and liver, while significantly lower expression (p > 0.05) was found in spleen, P. Kidney and skin (Fig. 3A).


Structural and functional characterization of salmon STAT1, STAT2 and IRF9 homologs sheds light on interferon signaling in teleosts.

Sobhkhez M, Skjesol A, Thomassen E, Tollersrud LG, Iliev DB, Sun B, Robertsen B, Jørgensen JB - FEBS Open Bio (2014)

Relative gene expression of STAT2a/b and IRF9 in tissues from healthy Atlantic salmon The relative expression of STAT2a/b (A) and IRF9 (B) in the tissues heart, gill, intestine, spleen, posterior kidney (P. Kidney), head kidney (H. K), liver, skin, thymus and muscle were measured by qPCR and presented relative to EFlαβ by the formula (ctEFlαβ)/(ct of STAT2 or IRF9) Samples from 6 fish were analyzed and error bars represents the mean ±SD.
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4215117&req=5

f0015: Relative gene expression of STAT2a/b and IRF9 in tissues from healthy Atlantic salmon The relative expression of STAT2a/b (A) and IRF9 (B) in the tissues heart, gill, intestine, spleen, posterior kidney (P. Kidney), head kidney (H. K), liver, skin, thymus and muscle were measured by qPCR and presented relative to EFlαβ by the formula (ctEFlαβ)/(ct of STAT2 or IRF9) Samples from 6 fish were analyzed and error bars represents the mean ±SD.
Mentions: Tissues taken from healthy Atlantic salmon (heart, gill, intestine, spleen, posterior kidney (P. Kidney), head kidney (HK), liver, skin, thymus and muscle) were analyzed by qPCR using primer pairs detecting both STAT2a/b isoforms and IRF9 (Table 1). Results showed that STAT2a/b and IRF9 were expressed in all tissues tested. STAT2a/b revealed the highest relative expression in heart, gill, intestine, HK, muscle and liver, while significantly lower expression (p > 0.05) was found in spleen, P. Kidney and skin (Fig. 3A).

Bottom Line: Overexpression of STAT2a or STAT2b together with STAT1a activated a GAS-containing reporter gene construct in IFNγ-stimulated cells.The highest induction of GAS promoter activation was found in IFNγ-stimulated cells transfected with IRF9 alone.Taken together, these data suggest that salmon STAT2 and IRF9 may have a role in IFNγ-induced signaling and promote the expression of GAS-driven genes in bony fish.

View Article: PubMed Central - PubMed

Affiliation: The Norwegian College of Fishery Science, UiT The Arctic University of Norway, N-9037 Tromsø, Norway.

ABSTRACT
Mammalian IRF9 and STAT2, together with STAT1, form the ISGF3 transcription factor complex, which is critical for type I interferon (IFN)-induced signaling, while IFNγ stimulation is mediated by homodimeric STAT1 protein. Teleost fish are known to possess most JAK and STAT family members, however, description of their functional activity in lower vertebrates is still scarce. In the present study we have identified two different STAT2 homologs and one IRF9 homolog from Atlantic salmon (Salmo salar). Both proteins have domain-like structures with functional motifs that are similar to higher vertebrates, suggesting that they are orthologs to mammalian STAT2 and IRF9. The two identified salmon STAT2s, named STAT2a and STAT2b, showed high sequence identity but were divergent in their transactivation domain (TAD). Like STAT1, ectopically expressed STAT2a and b were shown to be tyrosine phosphorylated by type I IFNs and, interestingly, also by IFNγ. Microscopy analyses demonstrated that STAT2 co-localized with STAT1a in the cytoplasm of unstimulated cells, while IFNa1 and IFNγ stimulation seemed to favor their nuclear localization. Overexpression of STAT2a or STAT2b together with STAT1a activated a GAS-containing reporter gene construct in IFNγ-stimulated cells. The highest induction of GAS promoter activation was found in IFNγ-stimulated cells transfected with IRF9 alone. Taken together, these data suggest that salmon STAT2 and IRF9 may have a role in IFNγ-induced signaling and promote the expression of GAS-driven genes in bony fish. Since mammalian STAT2 is primarily an ISGF3 component and not involved in IFNγ signaling, our finding features a novel role for STAT2 in fish.

No MeSH data available.


Related in: MedlinePlus