Involvement of the catalytic subunit of protein kinase A and of HA95 in pre-mRNA splicing.
Protein kinase A (PKA) is a holoenzyme consisting of two catalytic (C) subunits bound to a regulatory (R) subunit dimer. Stimulation by cAMP dissociates the holoenzyme and causes translocation to the nucleus of a fraction of the C subunit. Apart from transcription regulation, little is known about the function of the C subunit in the nucleus. In the present report, we show that both Calpha and Cbeta are localized to spots in the mammalian nucleus. Double immunofluorescence analysis of splicing factor SC35 with the C subunit indicated that these spots are splicing factor compartments (SFCs). Using the E1A in vivo splicing assay, we found that catalytically active C subunits regulate alternative splicing and phosphorylate several members of the SR-protein family of splicing factors in vitro. Furthermore, nuclear C subunits co-localize with the C subunit-binding protein homologous to AKAP95, HA95. HA95 also regulates E1A alternative splicing in vivo, apparently through its N-terminal domain. Localization of the C subunit to SFCs and the E1A splicing pattern were unaffected by cAMP stimulation. Our findings demonstrate that the nuclear PKA C subunit co-locates with HA95 in SFCs and regulates pre-mRNA splicing, possibly through a cAMP-independent mechanism.
Kvissel
Anne-Katrine
AK
Department of Nutrition, University of Oslo, Oslo, Norway. a.k.kvissel@basalmed.uio.no
Ørstavik
Sigurd
S
Eikvar
Sissel
S
Brede
Gaute
G
Jahnsen
Tore
T
Collas
Philippe
P
Akusjärvi
Göran
G
Skålhegg
Bjørn Steen
BS
D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D020134:Catalytic Domain; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000201:enzymology; D000242:Cyclic AMP / Q000494:pharmacology; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits; D017868:Cyclic AMP-Dependent Protein Kinases / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation; D012322:RNA Precursors / Q000378:metabolism*; D012326:RNA Splicing / Q000187:drug effects
D054758:A Kinase Anchor Proteins; C485099:AKAP8 protein, human; D048868:Adaptor Proteins, Signal Transducing; D012322:RNA Precursors; D000242:Cyclic AMP; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits; D017868:Cyclic AMP-Dependent Protein Kinases; C517757:PRKACA protein, human; C517760:PRKACB protein, human