Linear selection markers are ideal for cotransfection with any expression vector where stable integration and expression are required. We offer linear selection markers for either hygromycin (Linear Hygromycin Marker) or puromycin (Linear Puromycin Marker) resistance. These markers are short, purified linear DNA fragments comprised of the marker gene, an SV40 promoter, and the SV40 polyadenylation signal.

Cotransfection of a linear selection marker achieves a higher number of positive clones than using either a single response vector containing a selection marker or cotransfecting with a circular selection marker. Linear selection markers are cotransfected at a decreased ratio relative to the expression vector (i.e., 20-fold less of the linear marker).

The pTK-Hyg Vector and the pPur Vector may be used to select for stably transformed mammalian cells using hygromycin and puromycin, respectively. When cotransfected with pTRE2 or a pBI vector, pTK-Hyg is especially useful for selecting double-stable Tet-On or Tet-Off Cell Lines. When integrated into the host cell’s genome, pTK-Hyg does not cause unwanted activation of pTRE- and pBI-derived plasmids because the HSV TK promoter lacks an enhancer element.