  Magnetoresistance measurements have been performed on a gated two-dimensional
electron system (2DES) separated by a thin barrier layer from a layer of InAs
self-assembled quantum dots (QDs). Clear features of the quantum Hall effect
were observed despite the proximity of the QDs layer to the 2DES. However, the
magnetoresistance ($\rho_{xx}$) and Hall resistance ($\rho_{xy}$) are
suppressed significantly in the magnetic field range of filling factor $\nu<1$
when a positive voltage is applied to the front gate. The influence of the
charge state in QDs was observed on the transport properties of the nearby 2DES
only in the field range of $\nu < 1$. It is proposed that the anomalous
suppression of $\rho_{xx}$ and $\rho_{xy}$ is related to spin excitation, which
is induced by spin-flip processes involving electrons in the QDs and the 2DES.
