The nation’s largest union representing health care employees will relocate its headquarters from Dorchester to North Quincy in June after leasing 41,549 square feet at 108 Myrtle St.

1199 SEIU United Healthcare Workers East will move from 150 Mount Vernon St. in Dorchester to the newly renovated 108 Myrtle St., which is owned by Campanelli Trigate Myrtle Quincy LLC.

The 160,882-square-foot building received recent capital improvements included an updated lobby, new energy management system and new gym and cafe.

The class A structure built in 1988 was previously occupied by Blue Cross Blue Shield of Massachusetts before the insurer relocated to a new complex in Hingham in 2007. Current tenants include GateHouse Media’s Propel Marketing, which signed a lease renewal and expansion for 38,700 square feet in August.

Braintree-based Campanelli has promoted the building as a lower-priced alternative to Boston office space, with rents in the Route 128 South market approximately 43 percent below those in the Financial District.

Newmark Grubb Knight Frank’s Jeremy Roy, Mike Edward and Leeanne Rizzo represented the union in the transaction. The team secured expansion, renewal, termination and signage rights for the 400,000-member union, according to a statement by Frank Borges, director of operations at 1199SEIU.