Development of an IP-Free Biotechnology Platform for Constitutive Production of HPV16 L1 Capsid Protein Using the Pichia pastoris PGK1 Promoter

Figure 2

Selection of well-expressing clones. P. pastoris transformants were subsequently subjected to higher drug levels (100, 500, and 1000 μg/mL zeocin) for screening of multicopy strains. (a) Secretion of HPV L1 protein from the P. pastoris/pPGKΔ3α/L1 clones resistant to 1000 μg/mL zeocin was detected by colony blot. Absence of detection in the P. pastoris strains controls (yeasts transformed with the parental vectors) ensured the reliability of the reaction. (b) Intracellular expression of HPV L1 protein was confirmed in P. pastoris/pPGKΔ3/L1 clones resistant to 1000 μg/mL zeocin by dot blot. HPV16 L1 protein episomally expressed in P. pastoris was used as positive control (dotted circle in white), while P. pastoris strain transformed with the empty vector was used as negative control (circle in white).

(a)

(b)