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DNA polymerase- α regulates type I interferon activation through cytosolic RNA:DNA synthesis

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ABSTRACT

Aberrant nucleic acids generated during viral replication are the main trigger for antiviral immunity, and mutations disrupting nucleic acid metabolism can lead to autoinflammatory disorders. Here we investigated the etiology of X-linked reticulate pigmentary disorder (XLPDR), a primary immunodeficiency with autoinflammatory features. We discovered that XLPDR is caused by an intronic mutation that disrupts expression of POLA1, the gene encoding the catalytic subunit of DNA polymerase-α. Unexpectedly, POLA1 deficiency results in increased type I interferon production. This enzyme is necessary for RNA:DNA primer synthesis during DNA replication and strikingly, POLA1 is also required for the synthesis of cytosolic RNA:DNA, which directly modulates interferon activation. Altogether, this work identified POLA1 as a critical regulator of the type I interferon response.

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Cytosolic RNA:DNA generation by POLA1 modulates nucleic acid sensor pathwaysqRT-PCR quantification of six ISGs after siRNA for Pola1 in MEFs from WT embryos or specific knockout strains, as indicated. *p<0.05 when compared to the corresponding conditions in WT MEFs (unpaired Student’s t test). Data are pooled from 4 independent experiments (mean and s.e.m.).
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Figure 7: Cytosolic RNA:DNA generation by POLA1 modulates nucleic acid sensor pathwaysqRT-PCR quantification of six ISGs after siRNA for Pola1 in MEFs from WT embryos or specific knockout strains, as indicated. *p<0.05 when compared to the corresponding conditions in WT MEFs (unpaired Student’s t test). Data are pooled from 4 independent experiments (mean and s.e.m.).

Mentions: Finally, we examined whether the effects of cytosolic RNA:DNA hybrids can be mapped to a specific nucleic acid sensor pathway upstream of TBK1. To test this question, we used primary mouse embryo fibroblasts with defects in key genes involved in nucleic acid sensing: Myd88−/−Ticam1−/− (Myd88 x TRIF double knockout), Tmem173−/− (Sting knockout), Cgas−/− (also known as Mb21d1 and encoding cGAS), and Mavs−/−. Using these cells, we found that Cgas−/− and Mavs−/− fibroblasts were particularly resistant to the effects of Pola1 siRNA (Fig. 7). Loss of other sensor pathways also partially rescued the phenotype associated with POLA1 deficiency. These findings suggest that cytosolic RNA:DNA preferentially regulates pathways upstream of MAVS and cGAS and may potentially have broader effects on other nucleic acid sensors.


DNA polymerase- α regulates type I interferon activation through cytosolic RNA:DNA synthesis
Cytosolic RNA:DNA generation by POLA1 modulates nucleic acid sensor pathwaysqRT-PCR quantification of six ISGs after siRNA for Pola1 in MEFs from WT embryos or specific knockout strains, as indicated. *p<0.05 when compared to the corresponding conditions in WT MEFs (unpaired Student’s t test). Data are pooled from 4 independent experiments (mean and s.e.m.).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4836962&req=5

Figure 7: Cytosolic RNA:DNA generation by POLA1 modulates nucleic acid sensor pathwaysqRT-PCR quantification of six ISGs after siRNA for Pola1 in MEFs from WT embryos or specific knockout strains, as indicated. *p<0.05 when compared to the corresponding conditions in WT MEFs (unpaired Student’s t test). Data are pooled from 4 independent experiments (mean and s.e.m.).
Mentions: Finally, we examined whether the effects of cytosolic RNA:DNA hybrids can be mapped to a specific nucleic acid sensor pathway upstream of TBK1. To test this question, we used primary mouse embryo fibroblasts with defects in key genes involved in nucleic acid sensing: Myd88−/−Ticam1−/− (Myd88 x TRIF double knockout), Tmem173−/− (Sting knockout), Cgas−/− (also known as Mb21d1 and encoding cGAS), and Mavs−/−. Using these cells, we found that Cgas−/− and Mavs−/− fibroblasts were particularly resistant to the effects of Pola1 siRNA (Fig. 7). Loss of other sensor pathways also partially rescued the phenotype associated with POLA1 deficiency. These findings suggest that cytosolic RNA:DNA preferentially regulates pathways upstream of MAVS and cGAS and may potentially have broader effects on other nucleic acid sensors.

View Article: PubMed Central - PubMed

ABSTRACT

Aberrant nucleic acids generated during viral replication are the main trigger for antiviral immunity, and mutations disrupting nucleic acid metabolism can lead to autoinflammatory disorders. Here we investigated the etiology of X-linked reticulate pigmentary disorder (XLPDR), a primary immunodeficiency with autoinflammatory features. We discovered that XLPDR is caused by an intronic mutation that disrupts expression of POLA1, the gene encoding the catalytic subunit of DNA polymerase-&alpha;. Unexpectedly, POLA1 deficiency results in increased type I interferon production. This enzyme is necessary for RNA:DNA primer synthesis during DNA replication and strikingly, POLA1 is also required for the synthesis of cytosolic RNA:DNA, which directly modulates interferon activation. Altogether, this work identified POLA1 as a critical regulator of the type I interferon response.

No MeSH data available.


Related in: MedlinePlus