Three of Washington's most successful art dealers will move their galleries from Georgetown and the P Street Strip to a long-abandoned building amid the empty shops and shoe stores of 7th Street downtown.

By July 1, Harry Lunn of Georgetown, Nancy McIntosh of the Protetch-McIntosh Gallery and Ramon Osuna of the Osuna Gallery (once known as the Pyramid) will relocate, suggesting a shift in the center of gravity of this city's commercial art scene.

The large high-ceilinged building they will renovate in partnership is at 406 7th St. N.W., a block from Pennsylvania Avenue and halfway between the National Portrait Gallery-National Collection of Fine Arts and the museums on the Mall.

Art mover Bob Lennon (who calls his shipping firm Artransport) organized the deal. Lennon, long involved in art real estate developments in both high-and-low-rent districts here, is one of the few men on the art scene able to involve competing dealers in cooperative projects.

Lennon, a partner in Gallery Row, a larger redevelopment project across the street on Seventh Street, says that "Gallery Row is in a holding pattern. Its opening is now at least two years away." Lennon also owns Hanover Square, on the unit block of N Street NW, a warehouse complex whose 200,000 square feet of not-yet-renovated space he expects to rent, or sell, as studios for artists.

Built in 1921, the three-story, 21,000-square-foot building on 7th Street (which once housed a dime store) has been rented from the U.S. Theater Corporation -- for approximately $5 per square foot -- on an eight-year lease.

McIntosh and Osuna will share the second floor. Lunn has rented half of the third floor. The remaining spaces on the first and third floors "are still up for grabs," says Lennon. "They will be leased to other galleries."

Washington architect David Schwartz has designed the $300,000 renovation. He has given each of the galleries carpeted floors, round columns sheated in plaster, and white angled walls, some of which will rotate. Schwartz says that construction may begin next week.

Though many art groups now rent space downtown, in the Lansburg building and elsewhere, it is uncertain whether they will stay there once rents begin to rise. "Washington is big enough for only one commercial art center," says Lennon. "Space costs $20 per square foot on P Street, but only a quarter of that downtown. The Metro is running, Pennsylvania Avenue is being redeveloped, the museums are already there. Attracting visitors is a cinch. The galleries are going to have to move downtown."