Bank of New York Mellon Corp. BK -0.52% , the nation’s oldest bank, is making the leap into the market for cryptocurrencies. The custody bank said Thursday it will hold, transfer and issue bitcoin and other cryptocurrencies on behalf of its asset-management clients. In time, BNY Mellon will allow those digital assets to pass through the same plumbing used by managers’ other, more traditional holdings—from Treasurys to technology stocks—using a platform that is now in prototype. The bank is already discussing plans with clients to bring their digital currencies into the fold. “Digital assets are becoming part of the ... (full story)