UPDATE 1-Japan's Yoshimoto Kogyo says to go private

* Yoshimoto says faces slowdown in contents market

* TV broadcasters seeking to produce shows at low cost

By Emi Emoto and Yumiko Nishitani

TOKYO, Sept 11 (Reuters) - Japanese entertainment agency Yoshimoto Kogyo Co Ltd 9665.OS said on Friday it planned to go private in a $554 million buyout led by a consortium that includes five TV broadcasters.

Yoshimoto, a major player in Japanese show business and agent for many of the country's most popular celebrities, said a slowdown in the contents market meant it faced a challenging business environment.

TV broadcasters, hit by falling advertisement revenues, were seeking to produce shows at low cost, it added.

The consortium of 14 firms, which include broadcaster Fuji Media Holdings (4676.T) and mobile phone carrier Softbank Corp (9984.T), will pay 1,350 yen per share in a tender offer from Sept. 14 to Oct. 29.

The buyout is the 11th biggest deal in which a listed Japanese firm has gone private since 2000.

Nobuyuki Idei, who once led Sony Corp (6758.T), will serve as the consortium's strategy adviser.

Other members of the consortium include Nippon Television Network Corp (9404.T), Tokyo Broadcasting System Holdings Inc (9401.T), TV Asahi Corp (9409.T) and TV Tokyo Corp 9411.T and advertising giant Dentsu Inc (4324.T).

Construction firm Taisei Corp (1801.T), brokerage firm Iwai Securities (8707.T) and mobile communication contents and technology firm Faith Inc (4295.T) are also members.

Prior to the announcement, Yoshimoto Kogyo shares rose 3.8 percent to 1,341 yen after Reuters reported details of its plans to go private. [ID:nT231810]

For the year ended in March, Yoshimoto Kogyo had an operating profit of 4.4 billion yen on revenue of 48.9 billion yen.

Yoshimoto Kogyo is based in the western Japanese city of Osaka where it started as a comedy theatre nearly 100 years ago. (Additional reporting by Taro Fuse; Editing by Edwina Gibbs)