Effect of Rac1 and Cdc42Hs effector
loop mutants on myogenin expression. (A) Parental L6, L6 RhoGV12, L6
Rac1V12, L6 Cdc42HsV12, and L6 RhoAV14 myoblasts were transfected with
HA-tagged JNK. As a control, cells were transfected with empty vector
(pCDNA3). JNK activities in the cell lysates were measured by
immunocomplex kinase activity with the use of GST–c-Jun as a
substrate, as described in MATERIALS AND METHODS. The results are
presented as averages for three independent experiments. (B) L6
myoblasts were cotransfected with HA-JNK and GFP-Rac1L61,
GFP-Rac1L61F37A, GFP-Rac1L61Y40C, GFP-Cdc42HsL61, GFP-Cdc42HsL61F37A,
or GFP-Cdc42HsL61Y40C. JNK activity in the cell lysates was measured as
described in MATERIALS AND METHODS. The results are presented as
averages for three independent experiments. (C) L6 myoblasts were
transfected with constructs expressing Myc-Rac1L61 (a and b),
Myc-Rac1L61F37A (c and d), Myc-RacL61Y40C (e and f), Myc-Cdc42HsL61 (g
and h), Myc-Cdc42HsL61F37A (i and j), or Myc-Cdc42HsL61Y40C (k and l).
After transfection, cells were induced to differentiate by the addition
of DM, fixed 1–2 d later, and processed for Myc epitope detection (a,
c, e, g, i, and k) and myogenin expression (b, d, f, h, j, and l). For
each panel, cells shown are representative of five independent
experiments with more than 100 observed cells. Bar, 10 μm. (D)
Summary of the quantification for myogenin expression in cells
transfected with empty pEGFP-C1, GFP-tagged Rac1V12 or Cdc42HsV12, or
Myc-tagged Rac1L61, Rac1L61F37A, Rac1L61Y40C, Cdc42HsL61,
Cdc42HsL61F37A, or Cdc42HsL61Y40C.