Insertion of the IgH locus 3' regulatory palindrome in expression vectors warrants sure and efficient expression in stable B cell transfectants.

We have explored the effect of inserting 3' immunoglobulin heavy chain (IgH) locus transcriptional regulatory elements in stable expression vectors driven by a heavy chain variable gene promoter (pVH). A cassette was constructed, associating three enhancer elements from the palindromic part of the 3' IgH regulatory region, namely Calpha3'/hs3 reverse, alpha3'E/hs1-2, and hs3. As regard to stable expression, this cassette carried some features of a locus control region (LCR) and conferred expression to an associated cat reporter gene in the majority of B cells having integrated the transgene. The palindromic cassette was inserted in an expression vector carrying Ig light chain coding sequences. In this construct, transcription driven by a pVH promoter/Emu cassette upstream of the transcription initiation site was boosted by the palindromic cassette located downstream of the coding sequence. This potent expression plasmid mimicking the architecture of endogenous Ig loci, definitely manifested a potent stimulatory activity for stable transcription, outscoring conventional ubiquitous or B-cell specific expression vectors.