NP9 PROTEIN OF THE
HUMAN ENDOGENOUS RETROVIRUS K INTERACTS WITH LNX (LIGAND OF NUMB PROTEIN X)
N.
Mueller-Lantzsch
We have recently identified
Np9 as a novel nuclear protein produced by the human endogenous retrovirus K
(HERV-K) and were able to document the exclusive presence of np9
transcript in tumors and transformed cells. With the aim to study whether Np9
has a role in tumorigenesis, a systematic search for interacting proteins was
performed. Here, we identify the Ring-type E3 ubiquitin ligase LNX (ligand of
Numb protein X) as an NP9-interacting partner and show that association between
the two proteins can affect the subcellular localization of LNX. LNX has been
reported to target the cell fate determinant and Notch-antagonist Numb for
proteasome-dependent degradation, thereby causing an increase in
transactivational activity of Notch. We document that LNX-interacting Np9, like
Numb, is unstable and degraded via the proteasome pathway. Combined, this
points to the possibility that Np9 affects tumorigenesis through the LNX/Numb/Notch
pathway.