FIG. 4.

Small population of Ik-1-expressing cells are arrested at G₀/G₁. (A) Three days after infection of the JE131 cells with MSCV-IRES-H-2Kk (Ik−), MSCV-(Ik-7)-IRES-H-2Kk (Ik-7), or MSCV-(Ik-1)-IRES-H-2Kk (Ik-1) retrovirus, DNA content was analyzed by propidium iodide staining as a measure of cell cycle status. Cells that fall into the R1 gate show similar cell cycle profiles in all three transduced cultures. However, the unique small cell population (R2) observed in the Ik-1-transduced culture is blocked at the G₀/G₁ phase of the cell cycle. (B) At day 6 postinfection, successfully transduced cells were sorted from the cultures, and Pyronin Y staining was performed to measure cytoplasmic RNA content. Pyronin Y-negative cells are in G₀, whereas Pyronin Y-positive cells are in G₁, S, or G₂/M phase. The majority of Ik-1-transduced cells fell into the small cell population and failed to stain with Pyronin Y. This figure was generated by using CellQuest and Adobe Photoshop software.