  We consider a minimal renormalizable non-supersymmetric $E_6$ Grand Unified
Theory using fundamental representation $27$ for fermions and scalars. The
scalar with adjoint representation ${78}$ is also taken for direct breaking of
$E_{6}$ to SM. The proposed model, guided by TeV-scale vector-like fermions and
scalar leptoquark offer successful gauge unification even in the absence of any
intermediate symmetry. Embedded with threshold corrections, it is shown to be
compatible with the present experimental limit on proton decay lifetime. The
unique feature of the model shows that, the GUT threshold corrections to the
unification mass, is controlled by superheavy gauge bosons only, thereby
minimising the uncertainty of the GUT predictions. The scalar leptoquark and
vector-like fermions residing in $27$ representation can explain flavor physics
anomalies like $R_{D^{(\ast)}}$ as reported by the LHCb collaboration and the
muon anomalous magnetic moment reported by the recent muon $g-2$ experiment at
Fermilab. The model can also predict a sub-eV scale neutrino at one-loop level
via exchange of $W$ and $Z$ gauge bosons through MRIS mechanism.
