Polypeptide expression systems

A nucleic acid molecule comprising a set of splice sites consisting of a first 5′ splice site (5′ss11), a second 5′ splice site (5′ss12), and a 3′ splice site (3′ss11), the nucleic acid comprising a first expression cassette, the first expression cassette comprising the following components:

• (a) a first eukaryotic promoter (P1Euk1);
• (b) a first excisable prokaryotic promoter module (ePPM1) comprising the following components:
• (i) the 5′ss12;
• (ii) a prokaryotic promoter (P1Prok1);
• and
• (iii) the 3′ss11,
• wherein the components of the ePPM1 are operably linked to each other in a 5′-to-3′ direction as 5′ss12-P1Prok1-3′ss11;
• (c) a first polypeptide-encoding sequence (PES11);
• (d) the 5′ss11;
• and
• (e) a utility peptide-encoding sequence (UPES), wherein the UPES encodes all or a portion of a pill coat protein of bacteriophage M13, and wherein the UPES comprises a mutated polyadenylation site,
• wherein the components of the first expression cassette are operably linked to each other in a 5′-to-3′ direction as P1Euk1-ePPM1-PES11-5′ss11-UPES.

A nucleic acid molecule comprising a set of splice sites consisting of a first 5′ splice site (5′ss11), a second 5′ splice site (5′ss12), a third 5′ splice site (5′ss13), a first 3′ splice site (3′ss11), and a second 3′ splice site (3′ss12), wherein the nucleic acid molecule comprises:

• (a) a first expression cassette, the first expression cassette comprising the following components:
• (i) a first eukaryotic promoter (P1Euk1);
• (ii) a first excisable prokaryotic promoter module (ePPM1) comprising the 5′ss12, a prokaryotic promoter (P1Prok1), and the 3′ss11, wherein the components of the ePPM1 are operably linked to each other in a 5′-to-3′ direction as 5′ss12-P1Prok1-3′ss11;
• (iii) a first polypeptide-encoding sequence (PES11);
• (iv) the 5′ss11;
• and
• (v) a utility peptide-encoding sequence (UPES), wherein the UPES encodes all or a portion of a pill coat protein of bacteriophage M13, and wherein the UPES comprises a mutated polyadenylation site, and
• (b) a second expression cassette, the second expression cassette comprising the following components:
• (i) a second eukaryotic promoter (P1Euk2);
• (ii) a second excisable prokaryotic promoter module (ePPM2) comprising the 5′ss13, a prokaryotic promoter (P1Prok2), and the 3′ss12, wherein the components of the ePPM2 are operatively linked to each other in a 5′-to-3′ direction as 5′ss13-P1Prok2-3′ss12;
• (iii) a second polypeptide-encoding sequence (PES12);
• and
• (iv) a polyadenylation site (pA1),
• wherein the components are operably linked to each other in a 5′-to-3′ direction as P1Euk2-ePPM2-PES12-pA1-P1Euk1-ePPM1-PES11-5′ss11-UPES.