Boston-based private equity firm TA Associates announced on Thursday that it’s leading a buyout of Seattle-based Russell Investments’ asset-management business from London Stock Exchange Group PLC (LSE).

Reverence Capital Partners is joining TA Associates and will make a “significant minority investment” in Russell. Both TA and Reverence are longtime investors in the asset-management business.The transaction, which is valued at US$1.15 billion, is subject to customary closing adjustments and regulatory approval.

Russell Investments has US$266 billion in assets under management. The deal is expected to be completed in the first half of 2016. The LSE, which acquired Russell Investments for US$2.7 billion last year, also confirmed that the separation of Russell Investments’ index business from the asset-management business is expected to be completed in the first quarter of 2016, when the index division will be integrated fully with the FTSE.

“We are excited to work with the principals at TA Associates and Reverence Capital, firms we’ve been well acquainted with for many years,” says Len Brennan, president and CEO of Russell Investments, in a statement.

Brennan will continue to lead Russell Investments and will remain a member of its board. He will step down from the LSE’s executive committee upon the deal’s closing.

“TA Associates and Reverence Capital have extensive experience in asset management and we consider their decision to invest in Russell Investments a notable endorsement of our leading position in outcome-oriented solutions, one of the fastest-growing segments in the asset-management industry,” Brennan adds. “Through their financial backing, strategic guidance and industry expertise, TA Associates and Reverence Capital will support Russell Investments’ growth and help us continue to deliver innovative investment solutions to our global client base.”