H1 and HMG17 extracted from calf thymus nuclei are efficient DNA carriers in gene transfer.

In this article we describe the chromatographic separation of acid nuclear protein fractions which have previously been shown to be active in DNA transfection experiments. By combining anionic and cationic ion exchangers, we were able to separate and identify some of the active proteins. In addition to HMG1, already known for its transfection activity, we have identified histone H1 and HMG17 as further transfection-active proteins. The highest transfection activity was associated with H1 and another nonidentified protein showing a somewhat higher electrophoretic mobility than H1. We have also found that the presence of CaCl2 in a low concentration in the cell culture medium is an important requirement for transfection.