It's the end of an era for American television: the Queen Bee of daytime TV, Oprah Winfrey, announced last Friday that she will be quitting her self-titled talk show at the end of its 25th season in September 2011.

The 55-year-old billionaire is to shift her focus from network television to a new cable channel entitled the Oprah Winfrey Network (OWN). Just what exactly Winfrey's role in the new venture will be remains to be seen: according to the New York Times, Winfrey is expected to produce new programmes for OWN, and will appear occasionally on some of them.

Critics and industry watchers have been saying for a few years now that Winfrey's talk show was losing its lustre. Ratings were down, as were advertising rates, though Winfrey's interview last week with former US vice-presidential candidate Sarah Palin represented a storming return to form.

There has been speculation that Winfrey was looking to spread her wings.

Of course, she had already made moves into journalism (her lifestyle magazine O), publishing (her Book Club can turn authors into millionaires overnight), and film production (she's a producer of the upcoming movie Precious: based on the novel Push by Sapphire, which is hotly tipped for Oscar glory).

But perhaps her most significant career stretch so far was the decision to endorse -- and campaign alongside -- Barack Obama for president in 2007, back in the early stages of his epic primary battle against Hillary Clinton.

Earlier this year there was speculation that Winfrey might be appointed by President Obama as a US ambassador, and those fond of conspiracy theories will no doubt be intrigued that the timing of Winfrey's talk-show retirement -- the end of 2011 -- will dovetail neatly with Obama's re-election campaign in 2012.

Whatever she does next though, her departure from the talk show will be a huge cultural milestone in American life -- an "aha moment" as the lady herself is wont to say.

Born into poverty in rural Mississippi in 1954, Winfrey's harrowing childhood has been viewed as the cornerstone of both her ability to empathise with others, and her vast ambition. As a child, Winfrey was molested by her cousin, uncle and a family friend, all of which she publicly admitted live on TV during a discussionabout sexual abuse.

Having won the Miss Black Tennessee beauty pageant at age 17, Winfrey worked in local media, before being headhunted by TV execs in Chicago. The Oprah Winfrey Show first aired in 1986, and heralded the beginning of the modern phenomenon of "confessional television".

Of course, Oprah herself had something else that endeared her to viewers: her own very public battle with her fluctuating weight. She never shied away from discussing it -- particularly when it peaked at 238lbs (17 stone) -- and, after losing 67 pounds in 1988, Winfrey opened an episode of the show by pulling out a trolley holding the equivalent of the weight loss in animal fat.

In her 25 years in the business, Winfrey has turned into a multimedia giant, becoming the first African-American dollar billionaire, and indisputably the most powerful woman in America. In addition to her TV work, Winfrey is also an Oscar nominated actress, earning a nod for a powerful supporting role in Steven Spielberg's The Colour Purple.

Even as her show entered its second decade, Oprah managed to dominate the showbiz headlines, either by giving away free cars to the audience or landing exclusive interviews like her gut-wrenching chat with Kate and Gerry McCann last year.

The most famous -- or notorious -- episode of the past decade was her interview with Tom Cruise in 2005, in the course of which the actor manically jumped up on Oprah's couch to declare his love for Katie Holmes.

It hasn't all been plain sailing. Perhaps Oprah's lowest point came in 1996 when a group of Texas cattlemen sued her over remarks she made about beef during an episode focusing on mad cow disease. The men claimed that her comments caused the cost of beef to plummet, and sought reparations of $12m.

A jury found that Oprah and her team were not liable for damages, but even during that blip Oprah managed to use her Midas Touch to unearth a star: her counsellor at the time was one Dr Phil McGraw.

He subsequently became a regular on her show, before landing his own TV deal in 2002. If she can keep that magic touch, Oprah's presence will be felt long after she puts away the tissue box and hangs up the mic.

- Declan Cashin

Irish Independent