Characterization of the MAP Kinase Inhibition Domain of ST5 p70

The ST5 gene encodes three proteins with molecular
masses of 126, 82 and 70 kDa. The 126 kDa protein
contains domains suggestive of a role in regulating
signal transduction pathways and activates ERK2 MAP
kinase in response to EGF stimulation. This activity
is suppressed by p70. More recently, p70 expression
has demonstrated the ability to suppress baseline
ERK2 activation. In order to identify the p70 domain
which mediates suppression of ERK2 activity, HA-
tagged p70 variants were constructed and used with
HA-tagged ERK2 to co-transfect COS-7 cells. The
effects of these variants on ERK2 activity were
determined by performing an in vitro kinase assay,
and comparing these results to the inhibitory
effects of full-length p70. The results suggest that
the critical ERK2 inhibition domain comprises not
only a MADD homology domain, but also includes amino
acid residues immediately downstream of this region.
This region contains no MAPK docking domains, which,
along with the inability of p70 to bind directly to
ERK2, suggest that p70 mediates ERK2 suppression
indirectly through a presently unidentified protein.

Autorentext
Andrew Louden received the Ph.D. degree in genetics from Howard University with a research concentration in molecular biology. After graduating Howard, he accepted a postdoctoral position at the University of Pennsylvania School of Medicine where his research interest included HIV tropism.

Klappentext
The ST5 gene encodes three proteins with molecular masses of 126, 82 and 70 kDa. The 126 kDa protein contains domains suggestive of a role in regulating signal transduction pathways and activates ERK2 MAP kinase in response to EGF stimulation. This activity is suppressed by p70. More recently, p70 expression has demonstrated the ability to suppress baseline ERK2 activation. In order to identify the p70 domain which mediates suppression of ERK2 activity, HA- tagged p70 variants were constructed and used with HA-tagged ERK2 to co-transfect COS-7 cells. The effects of these variants on ERK2 activity were determined by performing an in vitro kinase assay, and comparing these results to the inhibitory effects of full-length p70. The results suggest that the critical ERK2 inhibition domain comprises not only a MADD homology domain, but also includes amino acid residues immediately downstream of this region. This region contains no MAPK docking domains, which, along with the inability of p70 to bind directly to ERK2, suggest that p70 mediates ERK2 suppression indirectly through a presently unidentified protein.