JERSEY CITY, NJ — Mack-Cali Realty Corp. has closed on the latest addition to its Jersey City residential portfolio, acquiring a two-tower, 648-unit apartment complex for $409 million. The real estate investment trust, which is based in the city, announced in early August that it had agreed to acquire the Liberty Towers property at 33 Hudson St. It has now completed the acquisition of the twin 37-story buildings, which were built in 2003 and were among the first luxury apartment properties to usher in Jersey City’s waterfront residential boom. A brokerage team including Jose Cruz, Kevin O’Hearn, Michael Oliver, Stephen Simonelli, Mark Mahasky and Andrew Scandalios — formerly of HFF but now of JLL — marketed Liberty Towers on behalf of JP Morgan Asset Management. The deal comes five months after Mack-Cali acquired Soho Lofts, a 377-unit rental community in Jersey City’s emerging Soho West neighborhood, for $264 million. The REIT, through its Roseland Residential Trust subsidiary, has worked in recent years to expand its multifamily portfolio along the Hudson waterfront through both acquisition and construction.