{'fraction_non_alphanumeric': 0.02695489725113424, 'fraction_numerical': 0.004803843074459567, 'mean_word_length': 5.877064220183486, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Oncogenic Kaposi’s Sarcoma-Associated Herpesvirus Upregulates Argininosuccinate Synthase 1, a Rate-Limiting Enzyme of the Citrulline-Nitric Oxide Cycle, To Activate the STAT3 Pathway and Promote Growth Transformation

We have previously shown that Kaposi’s sarcoma-associated herpesvirus (KSHV)-transformed cells depend on glutamine rather than glucose for energy production and amino acid and nucleotide syntheses. In this study, we have further examined how the KSHV-reprogramed metabolic pathways are regulated and discovered that KSHV hijacks the citrulline-nitric oxide (NO) cycle to promote growth proliferation and transformation. Multiple KSHV-encoded microRNAs upregulate argininosuccinate synthase 1 (ASS1), a key enzyme in the citrulline-NO cycle. ASS1 is required for KSHV-induced proliferation, colony formation in soft agar, and NO generation of KSHV-transformed cells, which also depends on inducible nitric oxide synthase. By maintaining intracellular NO levels, ASS1 mediates KSHV activation of the STAT3 pathway, which is essential for KSHV-induced abnormal cell proliferation and transformation. These results illustrate a novel mechanism by which an oncogenic virus hijacks a key metabolic pathway to promote growth transformation and reveal a potential novel therapeutic target for KSHV-induced malignancies. ABSTRACT Cancer cells are required to rewire existing metabolic pathways to support their abnormal proliferation. We have previously shown that, unlike glucose-addicted cancers, Kaposi’s sarcoma-associated herpesvirus (KSHV)-transformed cells depend on glutamine rather than glucose for energy production and amino acid and nucleotide syntheses. High-level consumption of glutamine is tightly regulated and often coupled with the citrulline-nitric oxide (NO) cycle. We have found that KSHV infection accelerates nitrogen efflux by upregulating the expression of argininosuccinate synthase 1 (ASS1), a key enzyme in the citrulline-NO cycle. KSHV utilizes multiple microRNAs to upregulate ASS1 expression. Depletion of either ASS1 or inducible nitric oxide synthase (iNOS) in KSHV-transformed cells suppresses growth proliferation, abolishes colony formation in soft agar, and decreases NO generation. Furthermore, by maintaining intracellular NO levels, ASS1 expression facilitates KSHV-mediated activation of the STAT3 pathway, which is critical for virus-induced transformation. These results illustrate a novel mechanism by which an oncogenic virus hijacks a key metabolic pathway to promote growth transformation and reveal a potential novel therapeutic target for KSHV-induced malignancies. IMPORTANCE We have previously shown that Kaposi’s sarcoma-associated herpesvirus (KSHV)-transformed cells depend on glutamine rather than glucose for energy production and amino acid and nucleotide syntheses. In this study, we have further examined how the KSHV-reprogramed metabolic pathways are regulated and discovered that KSHV hijacks the citrulline-nitric oxide (NO) cycle to promote growth proliferation and transformation. Multiple KSHV-encoded microRNAs upregulate argininosuccinate synthase 1 (ASS1), a key enzyme in the citrulline-NO cycle. ASS1 is required for KSHV-induced proliferation, colony formation in soft agar, and NO generation of KSHV-transformed cells, which also depends on inducible nitric oxide synthase. By maintaining intracellular NO levels, ASS1 mediates KSHV activation of the STAT3 pathway, which is essential for KSHV-induced abnormal cell proliferation and transformation. These results illustrate a novel mechanism by which an oncogenic virus hijacks a key metabolic pathway to promote growth transformation and reveal a potential novel therapeutic target for KSHV-induced malignancies.