What it's like to host ''Big Brother'' -- Julie Chen opens up about hosting a summer reality series, marrying her boss, and earning a (derogatory?) nickname

All great newscasters coin a memorable catchphrase. Edward R. Murrow famously signed off with ”Good night, and good luck.” Walter Cronkite bid adieu with ”And that’s the way it is.” And whether she likes it or not, The Early Show coanchor Julie Chen is making her mark with two simple words: ”but first.”

A few examples from some of the kaffeeklatsch’s recent airings: ”Still ahead on The Early Show, the hilarious Wanda Sykes is going to be here telling us about her new movie called Over the Hedge — but first, let’s head over to Dave for another check of the weather.” That same day also brought ”There are important new guidelines women should follow before they get pregnant — we’ll have details ahead on HealthWatch. But first, here’s René.” Finally, ”Did you know you can take your pet to the pet wash? We’ll have that very cute story coming up in our next hour. But first, Taylor Hicks is savoring his victory as the next American Idol.”

Okay, so maybe it’s not as memorable as the old Huntley-Brinkley banter, but those guys never moonlighted on a summer reality show like Big Brother (returning July 6 at 8 p.m.). And unlike Chen, the gents certainly never inspired a viral Internet video that featured their sign-offs played ad nauseam. (For a compilation of Chen’s Big Brother ”but first” transitions, go to TVgasm). Indeed, Chen keeps her high heels planted in two disparate worlds — she’s a serious newswoman by day and the Big Brother host by night.

Plenty of TV journalists might treat a game show as an embarrassing footnote in an otherwise successful career. And Chen knows how her participation in a program that features Web-feed fornication may look to detractors. ”I truly feel the morning-show hosts are held to a different level of accountability,” says Chen, a genial, petite woman who, in person, looks far younger than her 36 years. ”After I started getting criticism for doing Big Brother, someone told me that Hugh Downs used to host Concentration and Mike Wallace used to do The Big Surprise. I thought, Huh, maybe that door isn’t sealed shut if I want to do 60 Minutes one day.”

You can’t blame the gal for dreaming — just look at new 60 Minutes correspondent Anderson Cooper, who hosted ABC’s The Mole. But maybe 60 Minutes isn’t such a big dream — did we mention that Chen is also married to her boss Leslie Moonves, the CEO of CBS Corp. and one of the most powerful men in TV?

Newscaster, entertainer, the boss’ wife — Chen just might be navigating the trickiest celebrity career trajectory possible. Almost as tricky as securing an interview with her: It’s taken EW nearly three years to score a sit-down with Chen. Why did she and CBS acquiesce? Well, for one, Chen wants to promote her seventh go-round as a Big Brother host, especially since this installment is an all-star version featuring 12 of the most memorable former contestants. (The season kicks off June 21 at 8 p.m. with a prime-time special in which America will be asked to choose — from a pool of 20 — the housebound dolts who try to stay put the longest so that they can nab a $500,000 prize.)