Experimental setup and vectors. (A) Murine Lin^- cells were isolated, prestimulated, and transduced with cell-free vector supernatants with the use of MOIs, as indicated in Table 1. The cells were expanded as a mass culture for 2 weeks and subsequently selected on a 96-well plate (step 1). Randomly picked clones were further expanded to numbers exceeding 10⁶ for phenotyping and to harvest DNA and RNA (step 2). (B) Retroviral vectors used for transduction shown as proviruses. LTRSF is an LTR-driven retroviral vector that has been previously described (SF91).¹⁴  It contains a splice-competent leader region, including the primer binding site (θ) and the packaging signal (Ψ), and encodes either eGFP or DsRed. The U3 region containing all the enhancer/promoter elements is derived from spleen focus-forming virus (SF). SINSF is a self-inactivating (SIN) retroviral vector.¹⁵  The U3 region is almost completely deleted, leaving only the integrase attachment sites intact. eGFP and DsRed are driven by the SF enhancer/promoter, identical to the cis-elements used in the LTR-driven vector.