Abstract. Alcohol consumption is a predominant etiological factor in the pathogenesis of chronic liver diseases. The progressive nature of alcohol-associated liver disease (ALD) has been well described, but the complex interactions under which these pathologies evolve remain only partially elucidated. Based on our preliminary study, free nucleosides and nucleosides hydrolyzed from total RNA are altered in mice treated with alcohol and in a human liver cell line, HepaRG, treated with acetaldehyde. We also observed significant changes in the serum and urine of patients with different stages of ALD. Therefore, we hypothesize that alcohol consumption affects RNAs' chemical modification and contributes to ALD development and progression. To prove this hypothesis, we will treat mice with alcohol and first map the chemical modifications on RNAs by isolating different types of RNAs from mouse liver, digesting them into nucleosides and oligonucleotides, and detecting the site- specific modification on each RNA using comprehensive 2DLC-MS (Aim 1). And then, RNA modification variation will be studied between alcohol fed and normal fed mice at the RNA level, and the underlying mechanism will be uncovered by detecting the expression of the corresponding enzymes (Aim 2). 1