According to the invention, a structural domain reaction substrate sequence consisting of
Exon1 (E1), P1 and
Exon2 (E2) sequences of
ribozyme is mutated, and E1, P1 and E2 sequences are mutated under the condition of maintaining the
structural stability, so that the Azoarcus group I
intron ribozyme still has
enzyme activity and can maintain the capability of forming
circular RNA (
Ribose Nucleic Acid). The invention discloses a flexible vector construction method for preparing
circular RNA (Ribonucleic Acid) without limitation of a substrate sequence, which comprises the following steps: determining a target to-be-cyclized site sequence NNUNNNN, and segmenting the target to-be-cyclized site sequence NNUNNNN into E1: NNU and E2: NNNN; with E1 and E2 sequences as references, designing IGS sequences to respectively form complementary
pairing with E1 and E2; and 5'and 3 'homologous arms, IRES, CDS and other elements are respectively added. The method provided by the invention can be used for preparing the
circular RNA for any target sequence, has no residual sequence, and has relatively high cyclization efficiency. The FlexCirc cyclization
system designed on the basis of Azoarcus group I
intron ribozyme can form the circular
RNA, the cyclization substrate sequence has the characteristic of flexible design, and the cyclization efficiency can realize a relatively high cyclization proportion.