With regard to low levels of expression: Is there a particular reason
to use 293 cells? Transient expression in Cos-1/Cos-7 cells gives
~ 10 fold higher levels of expression because of the plasmid amplification
in these cells. (The only requirement is that the plasmid should
have SV40 ori; most mammalian vectors do).
HEK293T cells are reported to have high expression levels, especially
for secretted proteins (Aricescu et al., ACTA D, 2006).
Ah, yes, indeed. Like Cos cells, they do express large SV40 antigen,
so the transient expression levels will be high. I did not know about
it, thinking of "normal" 293 fibroblast line.
Dima
