NLS2APC-mediated nuclear translocation of βGal chimera is
regulated by phosphorylation at a PKA site. (A)
Alignment of NLS2APC with NLSSV40 T-ag reveals
similarity of NLS sequence as well as the adjacent putative
phosphorylation sites. (B) The NLS2APC
region is highly conserved among different species. NLS2 sequences are
bold; the CK2 and PKA sites are underlined. (C)
βGal-NLS2APC localizes to both the cytoplasm and nucleus
of L cells. βGal-NLS2APCmPKAS/A is
predominantly nuclear and βGal-NLS2APCmPKAS/D
predominantly cytoplasmic. (Bar = 10 μm.) Cells were scored as
above, and the incidence of nuclear staining for each βGal fusion is
as follows: βGal-NLS2APC, 69(±8)%;
βGal-NLS2APCmPKAS/A, 100(±0)%; and
βGal-NLS2APCmPKAS/D, 29(±6)%.
(D) Fractionation and Western immunoblot analysis of 293
cells transiently transfected with various constructs confirmed the
subcellular localization of the chimeric proteins. Fractions are
labeled as follows: C, cytosol; N, nuclear. The various cell fractions
were characterized by striping and reprobing the blot for the marker
proteins: lamin as a nuclear marker and rho as a cytoplasmic marker.