Mst1 regulates the CD19 transcriptional level. RT-PCR analysis of cd19 (A), cd21 (B), and btk (C) mRNA expression in fresh isolated B cells. Surface staining of CD19 (D) and CD21 (E) in fresh isolated B cells. Immunoblot of total Btk level in fresh isolated B cells (F). RT-PCR analysis of tead1, tead2, tead3, tead4 in fresh isolated B cells (G). Binding of TEAD2 to conserved motifs in the chr7:133 540 001-133 575  000 region (cd19 locus: chr7:133 551 962-133 558 384) in sorted CD19⁺ B cells from WT mice, analyzed by ChIP with antibody to TEAD2 (anti-TEAD2) or isotype-matched control antibody, IgG, followed by quantitative PCR; cyr 61 was used as a positive control (H). 293 cells were transfected with pcDNA3.1-tead2, pGL3-cd19-3′UTR, or pGL3-cd19-3′UTR-mutant and pRL-TKB (internal control) followed by luciferase reporter assay; pGL3-promoter and pGL3-basic were used as positive and negative controls (I). Splenocytes from WT and Mst1 KO mice were stimulated with or without sAg for 10 minutes followed by immunoblot of pMob1, total Mob1, pYap and total Yap, and Tead2 (J). RT-PCR analysis of mob (K), yap (L), tead2 (M) in fresh isolated splenocytes from WT and Mst1 KO mice. Shown are the representative images and results from 3 independent experiments. *P < .01, **P < .001.