NEW YORK (Reuters) - BrightSphere Investment Group BSIG.N is exploring a sale of its majority stake in Landmark Partners, a private equity fund investment firm that could be worth around $1 billion, people familiar with the matter said on Tuesday. The move underscores a push by BrightSphere"s largest shareholder, hedge fund Paulson & Co, to boost returns on its investment, after negotiations to sell BrightSphere to Italian financial firm Assicurazioni Generali GASI.MI earlier this year failed to produce a deal. BrightSphere has hired a financial adviser to work on a sale process for its 60% stake in Landmark, which specializes in buying and selling stakes in private equity and real estate funds, the sources said, cautioning that no deal is certain. The remaining 40% stake in Landmark is owned by its management. The sources requested anonymity because the matter is confidential. BrightSphere declined to comment, while Landmark did not respond to a request for comment. Boston-based BrightSphere had $185 billion in assets under management as of the end of September. The firm is a holding company for six asset management brands. It has a market capitalization of $1.3 billion. BrightSphere also held informal talks with interested parties in the summer about selling its quant manager Acadian, but it did not pursue a deal, the sources said. In July, it announced it would divest two investment businesses for $335 million in after-tax proceeds. Paulson & Co bought a 25% stake in BrightSphere in 2018 from Chinese conglomerate HNA Group. The head of the hedge fund, John Paulson, was elevated to chairman of BrightSphere in April.