Long non-coding RNA CARDINAL cis-activates MYOCD expression by recruiting histone reader ZZZ3 in vascular smooth muscle cell phenotype alteration.

AIMS: The phenotype alteration of vascular smooth muscle cells (VSMCs) is critical for vascular physiology and pathology. Transcription factors (TFs) and long non-coding RNAs (lncRNAs) play pivotal roles in the gene regulatory network underlying various biological processes, including the pathogenesis of vascular diseases. Despite the established role of Myocardin (MYOCD) as a master TF in VSMC biology, the MYOCD-mediated lncRNA-protein regulatory network in VSMC phenotype alteration remains elusive. Here, we explored lncRNAs potentially involved in MYOCD-dependent VSMC regulation.

METHODS AND RESULTS: We conducted an unbiased screening to identify key lncRNA regulators in this regulatory network using expression correlation analysis in diseased human arteries. As a result, we found that CARDINAL, a VSMC-enriched lncRNA located upstream of MYOCD, exhibited a strong positive expression correlation with MYOCD. Decreased CARDINAL expression was observed in atherosclerosis in both human and mouse models. Loss of CARDINAL induced phenotypic modulation in human VSMCs and promoted injury-induced neointima formation in mice. Gain-of-function of CARDINAL drove human VSMCs towards a contractile phenotype by activating MYOCD expression in a cis-regulatory manner. Mechanistically, CARDINAL recruited the ATAC histone acetyltransferase complex to the MYOCD promoter by interacting with the histone reader zinc finger ZZ-type containing 3 (ZZZ3). Subsequently, the complex increased histone acetylation at H3K4 and H3K9, thus activating the MYOCD promoter. Consequently, CARDINAL upregulated the expression of MYOCD and downstream contractile-related genes.

CONCLUSION: These findings unveil the importance of CARDINAL as a key lncRNA regulator of VSMC phenotype alteration and highlight its potential as an RNA target for therapeutic application in vascular diseases.