Story highlights 20 to 25 employees were laid off Friday from "The Tonight Show," a source says

Leno's salary reduction prevents even more job cuts, according to the source

The move is to shift the show from a prime time to late night cost structure, the source adds

Between 20 and 25 employees of NBC's "The Tonight Show" have been laid off and host Jay Leno has taken a substantial pay cut, a source with direct knowledge of the situation told CNN on Saturday.

The employees were let go Friday, with Leno's salary reduction intended to prevent even more staff reductions, the source said.

The actions were taken as NBC seeks to move the show to a cost structure typical of late-night programming, as opposed to prime-time shows, according to the source.

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Leno replaced the legendary Johnny Carson as host of "The Tonight Show" in 1992, a job he held for 17 years when he left in 2009 to helm "The Jay Leno Show" with a 10 p.m. start time. But a few months later, in January 2010, NBC announced the comedian would once again move to his old 11:35 p.m. time slot.

The Massachusetts-raised comic's venture into prime time three years ago was pitched as an attempt by the network to parlay his proven popularity into a commercially successful show.

But lagging ratings prompted NBC executives to change course within a few months. That move ultimately led to fellow talk show host Conan O'Brien's departure from the network. O'Brien now hosts a show, "Conan," on TBS that, like CNN, is a division of Time Warner.