miR-155 negatively regulates the transcription factor FOXO3, which positively regulates the pro-apoptotic factor BIM.

<p>(A) Negatively selected CD4^<b>+</b> T cells from WT and LAT-KI mice were stimulated with αCD3ε/CD4 (10 μg/ml) for the indicated times. Ages of the mice were 11 wks (WT), 7 and 11 wks (LAT-KI young and old). SDS WCLs were analyzed by WB (n = 5). (B) CD4^<b>+</b> T cell purification, stimulation and WB were as in Fig 4A. Ages of the mice were 11 wks (WT, LAT-KI) and 14 wks (miR155^<b>-/-</b>). SDS WCLs were analyzed by WB (n = 3). (C) CD4^<b>+</b> T cell purification, stimulation and WB were as in Fig 4A. Ages of the mice were 9 wks (WT), 12 wks (miR155^<b>-/-</b>, LAT-KI), and 14 wks (DM). SDS WCLs were analyzed by WB (n = 3). (D) miR-155 was overexpressed in mouse CD4^<b>+</b> cells by retroviral infection. Mock infection was performed as a negative control. In both cases, GFP was expressed to identify infected cells. Sorted GFP^<b>+</b>CD4^<b>+</b> T cells were stimulated with αCD3ε/CD4 (10 μg/ml) for 0, 3 or 10 min. SDS WCLs were analyzed by WB (n = 2).