AceShowbiz -

E. L. James finally puts an end to weeks of speculation circling around "Fifty Shades of Grey". The British author, whose bestseller of the same name will be adapted by Kelly Marcel, reveals on Twitter that the hotly-anticipated film has finally found its Anastasia Steele and kinky billionaire Christian Grey.

James, who also gets involved in the project from Focus Features as a producer, first tweets, "Good moaning all. Hold on to your hats..." The world's top-earning novelist adds, "I am delighted to let you know that the lovely Dakota Johnson has agreed to be our Anastasia in the film adaptation of Fifty Shades of Grey."

In another post, James reveals who has landed the coveted male role. "The gorgeous and talented Charlie Hunnam will be Christian Grey in the film adaptation of Fifty Shades of Grey," she shares the "Pacific Rim" actor's casting.

The first official casting announcements confirm The Wrap's report in August, which predicted that the "21 Jump Street" actress and the "Sons of Anarchy" hunk would be paired up.

Not long after the announcements, Johnson's mom Melanie Griffith takes to Twitter to express her excitement. "My beautiful child Dakota has been chosen to play Anna Steele in 50 Shades," she writes. "Look out world! Here she comes!!! #proudmama."

Co-producer Michael De Luca takes the opportunity to explain why the two were cast. "Auditions were stunning, incredible chemistry," De Luca tweets.

With Sam Taylor-Johnson serving behind the lens, the film will be released on August 1, 2014.