The mammalian high mobility group protein AT-hook 2 (HMGA2) is a multi-functional DNA-binding protein that plays important roles in tumorigenesis and adipogenesis. Previous results showed that HMGA2 is a potential therapeutic target of anticancer and anti-obesity drugs by inhibiting its DNA-binding activities. Here we report the development of a miniaturized, automated AlphaScreen ultra-high-throughput screening assay to identify inhibitors targeting HMGA2-DNA interactions. After screening the LOPAC1280 compound library, we identified several compounds that strongly inhibit HMGA2-DNA interactions including suramin, a century-old, negatively charged antiparasitic drug. Our results show that the inhibition is likely through suramin binding to the “AT-hook” DNA-binding motifs and therefore preventing HMGA2 from binding to the minor groove of AT-rich DNA sequences. Since HMGA1 proteins also carry multiple “AT-hook” DNA-binding motifs, suramin is expected to inhibit HMGA1-DNA interactions as well. Biochemical and biophysical studies show that charge-charge interactions and hydrogen bonding between the suramin sulfonated groups and Arg/Lys residues play critical roles in the binding of suramin to the “AT-hook” DNA-binding motifs. Furthermore, our results suggest that HMGA2 may be one of suramin’s cellular targets.

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The mammalian high mobility group protein AT-hook 2 (HMGA2) is a multi-functional DNAbinding protein which plays important roles in tumorigenesis and adipogenesis. Previous results showed that HMGA2 is a potential therapeutic target of anticancer and anti-obesity drugs by inhibiting its DNA-binding activities. Here we report the development of a miniaturized, automated AlphaScreen high throughput screening (HTS) assay to identify inhibitors targeting HMGA2-DNA interactions. After screening the LOPAC1280 compound library, we discovered that suramin, a negatively charged antiparasitic drug potently inhibits the HMGA2-DNA interaction. Our results also show that the inhibition is through suramin binding to the AT-hooks of HMGA2, therefore blocking its DNA binding capacity. Furthermore, we demonstrate that suramin can induce brain tumor stem cells differentiation into cells with neurite-like structures, a process triggered by disrupting HMGA2-DNA interactions. Since suramin has strong antitumor and anti-metastasis activities, our discovery suggests that HMGA2 and HMGA2-like proteins may be the cellular target of this century-old drug.The mammalian high mobility group protein AT-hook 2 (HMGA2) is a multi-functional nuclear protein associated with epithelial-to-mesenchymal transition (EMT) during embryonic development (1). Early studies showed that HMGA2 is related to preadipocyte proliferation and obesity (2-4). For example, Hmga2 knockout mice were severely deficient in fat cells and developed pygmy phenotype (5). The disruption of Hmga2 gene dramatically reduced obesity of leptin-deficient mice (Lep ob /Lep ob ) (2). These results suggest that HMGA2 is a potential target for the treatment of obesity. HMGA2 is also linked to oncogenesis. Its over and/or aberrant expression leads to the formation of a variety of tumors including benign tumors, such as lipomas (6), uterine leiomyomas (7), and fibroadenomas (8), and malignant tumors, such as lung cancer (9,10), breast cancer (11,12), prostate cancer (13), leukemia (14), and melanoma (15-18).Intriguingly, HMGA2 expression level always correlates with the degree of malignancy, metastasis, and a poor prognosis (19,20), suggesting that this protein is also a therapeutic target of anti-cancer and anti-metastasis drugs (21,22). Furthermore, HMGA2 is associated with neural and hematopoietic stem cell youth (23,24), human height (25), and human intelligence (26).HMGA2 is a small DNA-binding protein consisting of three "AT-hook" DNA binding motifs and a highly acidic C-terminal motif (27). These three "AT-hooks" contain a unique palindromic sequence, PGRGP, each side surrounded by one or two positively charged amino acids, i.e., Lysine or Arginine (28). HMGA2 is an intrinsically disordered protein (IDP (29)). When it binds to AT-rich DNA sequences, the "AT-hook" DNA binding motifs adopt defined structures (30).This disordered-to-ordered conformational transition allows HMGA2 to adapt to different ATrich DNA sequences and to participate in different nuclear activities, such as tra...

STING is a transmembrane ER resident protein that was initially described as a regulator of innate immune response triggered by viral DNA and later found to be involved in a broader range of immune processes. Here, we assessed its role in the antigen presentation by generating a STING KO macrophage cell line. In the absence of STING, we observed an impaired OVA-derived SIINFEKL peptide presentation together with a decreased level of MHC-I complex on the plasma membrane, likely due to a decreased mRNA expression of β2 m light chain as no relevant alterations of the peptide-loading complex (TAPs) were found. Moreover, JAK-STAT signaling resulted in impaired STING KO cells following OVA and LPS treatments, suggesting a dampened activation of immune response. Our data revealed a new molecular role of STING in immune mechanisms that could elucidate its role in the pathogenesis of autoimmune disorders and cancer.