Skadden, Arps, Slate, Meagher & Flom and Shearman & Sterling have the lead roles on Chinese micrcoblogging site Sina Weibo’s planned $500 million U.S. initial public offering.

Weibo was launched by Sina Corp. in 2009 as a Chinese version of Twitter. In 2010, competitors including Tencent Holdings Ltd, NetEase Inc. and Inc. also launched similar products, but Sina Weibo so far remains China’s largest and most influential microblogging service. The company reported 61.4 million daily active users at the end of December, accounting for over half of all microblog users in China.

Last April, Hangzhou-based e-commerce giant Alibaba Group invested $586 million in Sina Weibo, taking an 18 percent stake with an option to buy up to 30 percent in the future. Sina Weibo is now valued at $5.1 billion, according to Bloomberg.

Sina Weibo is being represented by Skadden Hong Kong partner Julie Gao, while underwriters Credit Suisse Group A.G. and Goldman Sachs Group Inc. are being advised by Shearman & Sterling Shanghai and Palo Alto partner Alan Seem.