Another historic downtown Boston office building is in line for a modernization program as the landlord seeks to attract new economy tenants.

After acquiring Ten Post Office Square last fall for $143 million, a joint venture of Synergy Investments and GreenOak Capital recently selected Boston-based architects Dyer Brown to design updates and renovations to common areas. The makeover is designed to attract tech tenants with an updated lobby, new central reception area and conversion of lower-level space into a fitness center, bicycle storage and locker rooms, said Roger Breslin, senior vice president for leasing agent JLL. Collaborative workspaces and new food vendors are also planned.

The 445,000-square-foot building is currently 82-percent leased. Boston Private Bank & Trust Co. is the largest tenant at approximately 150,000 square feet.

Downtown landlords are looking at the tech sector to fill vacancies in buildings primarily occupied by law offices, accountants and investment companies in past decades. Significantly higher rents and low vacancies in the Seaport and Fort Point have prompted tech companies to reconsider downtown locations. Burlington-based cloud computing company Acquia is moving to Exchange Place at 53 State St. this spring after leasing 73,000 square feet last fall.

“A lot of these companies would have never looked at the Class A or traditional buildings before,” Breslin said. “It feels like they’ve all kind of swooped into the market at the same time.”

For landlords, the downside is tech companies often prefer shorter 3- to 5-year leases and require custom build-outs.

The owners of Ten Post Office Square are sending out proposals in the mid-$40s per square foot range, reflecting the tightening market for Financial District office space.

Soundport Capital of New York, which previously owned Ten Post Office Square, spent over $17 million in the last seven years on capital improvements, according to Cushman & Wakefield, which brokered last year’s sale.