Plasmon-induced transparency (PIT) in nanostructures has been intensively investigated; however, there are no known metasurface nanostructures that exhibit all optically tunable properties, where the number of transparency windows can be tuned successively and switched to off-state. In this Letter, we theoretically investigate and demonstrate a dynamically tunable, multichannel PIT at optical frequencies. The in-plane destructive interference between bright and dark dipolar resonances in coupled plasmonic nanobar topologies is exploited to produce a tunable PIT with unique characteristics. In particular, we demonstrate a sequential polarization-selective multispectral operation whereby the number of PIT channels can be varied successively from 3 to 0. The results provide a promising route for an active manipulation of PIT and show potential applications for multifunctional dynamic nanophotonics devices.