Circular RNAs (circRNA) are evolutionarily conserved endogenous covalently closed molecules with diverse biological functions, described in various organisms,
including humans. In contrast to eukaryotic messenger RNAs (mRNAs), they are highly stable and resistant to exonucleases, rendering them potentially valuable for
diagnostic and therapeutic purposes. Their active role has been demonstrated in numerous (patho)physiological processes, such as insulin secretion, immune response, myocardial infarction, and cancer development. However, their involvement in circadian rhythm regulation remains underexplored. Therefore, we aimed to investigate their potential impact on the circadian rhythm by elevating the
expression of selected circRNA in the human U2OS cell line through transfection and monitoring the expression of one circadian gene using a luciferase reporter inserted into Bmal1 promoter. Using in silico tools, we predicted potential biological functions and associations with circadian rhythm proteins for the selected circRNAs. Upon reviewing the predicted associations in the literature, we highlight hsa_circZFP91_003 for its potential role in microRNA binding, potentially enhancing the expression of two circadian proteins (PML, PIWIL2). Additionally,
hsa_circMAN1A2_009 was implicated in microRNA and RBP binding, as well as translation into protein. Lastly, hsa_circRBM23_004 exhibited a potential role in mikroRNA binding and translation into two proteins. However, it is crucial to note that these findings are mere predictions, necessitating experimental validation to confirm real functional associations and roles of circRNA in circadian rhythm regulation. The first steps of experimental validation have already been outlined
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