LIN28A is a microRNA-binding protein that has been shown to bind the let-7 pre-microRNA and block production of mature let-7 in embryonic stem cells. This activity appears to preserve undifferentiated state of stem cells. LIN28A has been used to generate iPS cells. LIN28A lentivirus (TET-inducible, Hyg) expresses human LIN28 under the control of the Tet responsive promoter with hygromycin as a selection marker.