FIG. 1.

Expression constructs containing the L1 and L2 ORFs of HPV-16 with codons optimized for expression in human cells (L1h, L2h), plant cells (L1p), or with their original codons (L1ori, L2ori). In all constructs the expression of the capsid gene is driven by pCMV. To analyze the transient expressions of L1 and L2, the eukaryotic expression vector pUF3 was used (42) (a and d). This vector contains a small intron with a splice donor and splice acceptor site (SD/SA) located upstream of the respective capsid gene. (b) To analyze the influences of the various L1 genes on the expression of GFP (eGFP), bicistronic constructs in which the GFP gene was placed under the control of an IRES located downstream of the respective L1 gene were used. As a control, the L1 gene was replaced by the ecotropic retrovirus receptor gene rec1. (c) Expression construct containing L1ori in combination with the simian retrovirus CTE element cloned into the pcDNA 3.1 expression vector (Invitrogen).