TUBE is a fast food restaurant located in Portland Island, Liberty City and only made an appearance in Liberty City Stories. The sign is a clone of the fast food chain, Subway's.
Name
Since TUBE is a clone of Subway, the name was most likely chosen because in London, the Tube is equivalent to what a subway is called in the US. The first two letters (TU) are orange, and the last two (BE) are white opposed to Subway's yellow and white combination. The sign also has arrows coming off the 'T' and 'E' which is also like Subway's logo.
Opening Scene
During the opening cut-scene, TUBE can be seen in the background as Tony Cipriani exits the bus.