Engineered DNA molecule for coding RNA

An engineered DNA molecule capable of being replicated in a cell, comprising a polyadenosine tail (Poly A tail) coding sequence, wherein the structure of the poly (A) tail coding sequence is:

• 1) Element a-element d-element b-element c-element b-element c-element b;
• the element a is 60 nt in length, the element b is 16-19 nt in length, and the element d is 6 nt in length, or
• 2) Element b-element c-element b-element c-element b-element d-element a;
• and the element a is 60 nt in length, the element b is 16-19 nt in length, and the element d is 6 nt in length;
• wherein the element a consists of a plurality of consecutive adenine (A) nucleotides;
• the element b consists of a plurality of consecutive A nucleotides;
• the element c consists of a non-A nucleotide, and the nucleotide is selected from T, C and G nucleotides;
• and
• the element d consists of any two or more consecutive nucleotides, and the nucleotides are selected from A, T, C and G nucleotides, wherein the nucleotides at a 5′ terminus and a 3′ terminus of the element d are not A nucleotides, and the element d does not comprise 3 or more consecutive A nucleotides.

An RNA molecule encoded by an engineered DNA molecule capable of being replicated in a cell, wherein the engineered DNA molecule comprises a polyadenosine tail (Poly A tail) coding sequence, wherein the poly (A) tail coding sequence comprises:

• a single element a and at least one element b, and at least one element c and at least one element d:
• the element a consists of a plurality of consecutive adenine (A) nucleotides, and the length range of the element a is ≥20 nt and <80 nt;
• the element b consists of a plurality of consecutive A nucleotides, and the length range of the element b is 3 nt≤b<20 nt;
• the element c consists of a non-A nucleotide, and the nucleotide is selected from T, C and G nucleotides;
• the element d consists of any two or more consecutive nucleotides, and the nucleotides are selected from A, T, C and G nucleotides, wherein the nucleotides at a 5′ terminus and a 3′ terminus of the element d are not A nucleotides, the element d does not comprise 3 or more consecutive A nucleotides;
• and the length range of the element d is 2 nt≤d≤20 nt;
• and the element d comprises a palindromic sequence;
• wherein the element a and the element b are not adjacent, and the element c and the element d are not adjacent, and
• the poly (A) tail coding sequence does not comprise any two elements b that are adjacent to each other, does not comprise any two elements c that are adjacent to each other, and does not comprise any two elements d that are adjacent to each other.