The protein Nalpha-terminal acetyltransferase hNaa10p (hArd1) is phosphorylated in HEK293 cells.
BACKGROUND
The hNaa10p (hArd1) protein is the catalytic subunit of the human NatA Nalpha-terminal acetyltransferase complex. The NatA complex is associated with ribosomes and cotranslationally acetylates human proteins with Ser-, Ala-, Thr-, Val-, and Gly- N-termini after the initial Met- has been removed. In the flexible C-terminal tail of hNaa10p, there are several potential phosphorylation sites that might serve as points of regulation.


RESULTS
Using 2D-gel electrophoresis and hNaa10p specific antibodies, we have investigated whether hNaa10p is phosphorylated in HEK293 cells. Several differently charged forms of hNaa10p are present in HEK293 cells and treatment with Calf Intestine Alkaline Phophatase (CIAP) strongly suggests that hNaa10p is phosphorylated at multiple sites under various cell culture conditions. A direct or indirect role of GSK-3 kinase in regulating hNaa10p phosphorylation is supported by the observed effects of Wortmannin and LiCl, a GSK-3 activator and inhibitor, respectively.


CONCLUSIONS
We demonstrate that hNaa10p protein is phosphorylated in cell culture potentially pointing at phosphorylation as a means of regulating the function of one of the major Nalpha-terminal acetyltransferases in human cells.
Målen
Hiwa
H
Department of Molecular Biology, University of Bergen, N-5020 Bergen, Norway. hiwa.malen@gades.uib.no
Lillehaug
Johan R
JR
Arnesen
Thomas
T