System and method for screening rna aptamer

A method for screening an RNA aptamer against a target protein, comprising:

• (1) providing a screening cell, wherein the screening cell comprises a guide RNA, a target sequence, a selection marker, a fusion protein and a dCas protein, wherein the guide RNA comprises a recognition sequence and a nucleic acid aptamer random library having a predetermined length;
• the target sequence is complementary to the recognition sequence of the guide RNA;
• the selection marker is downstream of the target sequence and comprises a basal promoter and a selection marker gene;
• the fusion protein comprises the target protein and a transcriptional activation module, wherein a binding of the target protein to an RNA aptamer of the nucleic acid aptamer random library results in the recruitment of the transcriptional activation module to the selection marker;
• and the dCas protein specifically recognizes the target sequence under the guidance of the guide RNA;
• (2) screening the screening cell using the selection marker gene;
• (3) collecting the screening cell that expresses the selection marker gene;
• (4) lysing the screening cell, specifically amplifying a region containing the nucleic acid aptamer, and obtaining sequence information regarding the nucleic acid aptamer by sequencing and optionally analyzing and verifying the nucleic acid aptamer as obtained.