Parasitic Drain- Dome but effects radio and info display

[ggc]

My parents have a 2000 Lexus RX300.  About 6 months ago it developed a parasitic drain that would completely drain the battery if it sat for a few days.  I tested the current draw for all the fuses under the hood and found the DOME fuse was consistently drawing about 0.5 amps with the doors closed and the interior lights off.  I removed the DOME fuse and the battery has maintained its charge after sitting for several weeks.  Odd thing is that when I removed the DOME fuse, we lost power to the radio and the center information panel.  I don't know why the radio and information panel would be effected by the DOME circuit.  Is there a component that would interconnect the radio/information center to the Dome circuit? Thanks, Gilbert