You could use a P/N mosfet combo on the top side of the divider. P to switch power on/off to the divider, N so your uC can control the P without being pulled up to Vcc. P gate is pulled high and connected to N drain, N gate is pulled low and connected to uC pin. uC pin is high Z or low, N is off, P is off, voltage divider is off. uC pin is high, N is on, P is on, voltage divider is on.