Nuclear import of the myogenic factor MyoD requires cAMP-dependent protein kinase activity but not the direct phosphorylation of MyoD.
J Cell Sci
; 107 ( Pt 2): 613-20, 1994 Feb.
Article
in En
| MEDLINE
| ID: mdl-8207083
ABSTRACT
MyoD is a nuclear phosphoprotein that belongs to the family of myogenic regulatory factors and acts in the transcriptional activation of muscle-specific genes. We have investigated the role of cAMP-dependent protein kinase (A-kinase) in modulating the nuclear locale of MyoD. Purified MyoD protein microinjected into the cytoplasm of rat embryo fibroblasts is rapidly translocated into the nucleus. Inhibition of A-kinase activity through injection of the specific inhibitory peptide PKI prevents this nuclear localisation. This inhibition of nuclear location is specifically reversed by injection of purified A-kinase catalytic subunit, showing the requirement for A-kinase in the nuclear import of MyoD. Site-directed mutagenesis of all the putative sites for A-kinase-dependent phosphorylation on MyoD, substituting serine or threonine residues for the non-phosphorylatable amino acid alanine, had no effect on nuclear import of mutated MyoD. These data exclude the possibility that the effect of A-kinase on the nuclear translocation of MyoD is mediated by direct phosphorylation of MyoD and imply that A-kinase operates through phosphorylation of components involved in the nuclear transport of MyoD.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
MyoD Protein
/
Cyclic AMP-Dependent Protein Kinases
Limits:
Animals
Language:
En
Journal:
J Cell Sci
Year:
1994
Document type:
Article
Affiliation country:
France