Nuclear import of serum response factor in airway smooth muscle.
We have previously shown that the transcription-promoting activity of serum response factor (SRF) is partially regulated by its extranuclear redistribution. In this study, we examined the cellular mechanisms that facilitate SRF nuclear entry in canine tracheal smooth muscle cells. We used in vitro pull-down assays to determine which karyopherin proteins bound SRF and found that SRF binds KPNA1 and KPNB1 through its nuclear localization sequence. Immunoprecipitation studies also demonstrated direct SRF-KPNA1 interaction in HEK293 cells. Import assays demonstrated that KPNA1 and KPNB1 together were sufficient to mediate rapid nuclear import of SRF-GFP. Our studies also suggest that SRF is able to gain nuclear entry through an auxiliary, nuclear localization sequence-independent mechanism.
Department of Medicine, University of Chicago, 5841 S. Maryland Avenue, MC6026, Chicago, IL 60637, USA.
John F
JF
McConville
Darren J
DJ
Fernandes
Jason
J
Churchill
Samantha
S
Dewundara
Paul
P
Kogut
Shardul
S
Shah
Gregory
G
Fuchs
Dalius
D
Kedainis
Shashi K
SK
Bellam
Nina M
NM
Patel
Joel
J
McCauley
Nickolai O
NO
Dulin
Mahesh P
MP
Gupta
Stephen
S
Adam
Yoshihiro
Y
Yoneda
Blanca
B
Camoretti-Mercado
Julian
J
Solway
D021581:Active Transport, Cell Nucleus; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D019281:Dimerization; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008856:Microscopy, Fluorescence / Q000379:methods; D008954:Models, Biological; D009130:Muscle, Smooth / Q000166:cytology*; D009154:Mutation; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D026362:Serum Response Factor / Q000378:metabolism*; D028901:alpha Karyopherins / Q000378:metabolism
D011993:Recombinant Fusion Proteins; D026362:Serum Response Factor; D028901:alpha Karyopherins; D049452:Green Fluorescent Proteins