  We consider a class of $U(1)^\prime$-extended MSSM in which the
$U(1)^{\prime}$ symmetry is broken by vacuum expectation values (VEVs) of four
MSSM singlet fields. While one MSSM singlet field interacts with the MSSM Higgs
fields, three of them interact only with each other in forming a secluded
sector. Assigning universal $U(1)^{\prime}$ charges for three families, the
anomaly cancellation condition requires exotic fields which are assumed to be
heavy and decoupled. We discuss a variety of $U(1)^{\prime}$ charge assignments
and anomaly cancellation, $Z^{\prime}/Z$ hierarchy, neutralinos, charginos and
the Higgs sector. We find that the typical spectra involve two CP-odd Higgs
bosons lighter than about 200 GeV and 600 GeV respectively, which are mostly
formed by the MSSM singlet fields. If the relic density of dark matter is
saturated only by a neutralino, compatible solutions predict LSP neutralinos
formed by the MSSM singlet fields in the mass scales below about 600 GeV, while
it is possible to realize MSSM neutralino LSP above these mass scales. One can
classify the implications in three scenarios. Scenario I involves NLSP
charginos, while Scenario II involves charginos which do not participate
coannihilation processes with the LSP neutralino. These two scenarios predict
MSSM singlet LSP neutralinos, while Scenario I leads to larger scattering
cross-sections of dark matter. Scenario III has the solutions in which the MSSM
neutralinos are considerably involved in LSP decomposition which yields very
large scattering cross-section excluded by the direct detection experiments.
