p300, but not PCAF, collaborates with IRF-1 in stimulating TRIM22 expression independently of its histone acetyltransferase activity.

Tripartite motif ( TRIM) 22 plays an important role in IFN-mediated antiviral activity. We previously demonstrated that IFN regulatory factor-1 ( IRF-1) was crucial for constitutive and IFN-induced TRIM22 expression via binding to a special cis-element named 5′ extended IFN-stimulating response element. Here, we further investigate the molecular mechanisms of TRIM22 with a focus on the co-activators of IRF-1. Using an in vitro DNA affinity binding assay and an in vivo chromatin immunoprecipitation assay, we found that IFN-γ stimulation significantly enhanced the binding of p300 and p300/ CBP-associated factor, but not other co-activators such as general control nondepressible 5, steroid receptor co-activator-1, and activator of thyroid and retinoic, to the 5′ extended IFN-stimulating response element containing TRIM22 promoter region together with IRF-1. Overexpression and knockdown analysis demonstrated that it was p300, but not p300/ CBP-associated factor, that functioned as a transcriptional co-activator of IRF-1 in IFN-γ induction of TRIM22. We further show that p300 contributed to both IFN-γ- and IRF-1-mediated TRIM22 transcription independent of its histone acetyltransferase activity, however, it was required for the recruitment of RNA polymerase II to TRIM22 promoter region. These data indicate that p300 plays a critical role in IFN-γ-induced TRIM22 expression via recruiting RNA polymerase II to the TRIM22 promoter, and might serve as a bridge between IRF-1 and the basal transcriptional apparatus in TRIM22 induction. [ABSTRACT FROM AUTHOR]