(Reuters) - Former TikTok boss Kevin Mayer has joined Access Industries as a senior adviser for the investment group’s media portfolio. Mayer, who was also a high-profile executive at Disney, quit as chief executive officer of TikTok in August amid negotiations to sell its U.S. operations, just three months after his appointment. Access Industries, which has stakes in several firms including Warner Music Group, said Mayer will focus on its media, entertainment and telecommunications sectors to identify new investment opportunities. Japanese video game maker Nexon had said on Sunday that Mayer would join its board as an external director.