Dein, who was forced out of Arsenal in May, has been made chairman of Red and White and given the task of acquiring more shares.
Usmanov said in the Evening Standard: "I have been an Arsenal fan for eight years and I think the club has the best manager in the Premier League.
"But this purchase of mine is not a strategic or political one. It's a portfolio investment.
"Arsenal as a business is undervalued. My aim is to steadily increase my package because I think the value of it will grow and will soon reach a higher level. The club has everything to achieve it."
