This study investigates the role of microRNAs (miRNAs) in regulating gene expression through targeting non-coding antisense transcripts. Specifically, it focuses on miR-671, which targets the Cerebellar Degeneration-Related protein 1 (CDRI) locus in human cells. The research demonstrates that miR-671 directs Ago2-mediated cleavage of a circular antisense transcript of the CDRI locus, leading to a decrease in CDRI mRNA levels. This downregulation is independent of heterochromatin formation and provides the first evidence for non-coding antisense transcripts as functional miRNA targets. The study also reveals a novel regulatory mechanism involving a positive correlation between mRNA and antisense circular RNA levels. The findings highlight the importance of non-coding antisense transcripts in gene regulation and suggest a new role for miRNAs in nuclear gene silencing.This study investigates the role of microRNAs (miRNAs) in regulating gene expression through targeting non-coding antisense transcripts. Specifically, it focuses on miR-671, which targets the Cerebellar Degeneration-Related protein 1 (CDRI) locus in human cells. The research demonstrates that miR-671 directs Ago2-mediated cleavage of a circular antisense transcript of the CDRI locus, leading to a decrease in CDRI mRNA levels. This downregulation is independent of heterochromatin formation and provides the first evidence for non-coding antisense transcripts as functional miRNA targets. The study also reveals a novel regulatory mechanism involving a positive correlation between mRNA and antisense circular RNA levels. The findings highlight the importance of non-coding antisense transcripts in gene regulation and suggest a new role for miRNAs in nuclear gene silencing.