** Digital Realty's DLR.N shares down 2% in extended trading to $186.80 as co to increase its ownership in three Northern Virginia data centers

** DLR says to acquire a majority stake in three fully leased data centers from affiliates of Blackstone BX.N in deal valuing the assets at $7.8 bln

** DLR also announces $2.3 bln share offering by BX

** Offering shares comprise non-voting common stock to be issued to BX only upon the closing of the acquisition

** Morgan Stanley sole underwriter

** DLR shares ended down 1.3% at $190.58 on Mon, trimming YTD gain to 23%

** Austin, Texas-based DLR has ~351.4 mln shares outstanding for about $67 bln market cap