Yelp, the purveyor of online, crowd-sourced reviews about local businesses, signed a lease to take approximately 102,000 square feet of three-quarters of 55 Hawthorne St., an 11-story, 138,092-square-foot office building owned by Harvest Properties and Invesco Real Estate in downtown San Francisco. The pair purchased 55 Hawthorne and its adjacent neighbor, 631 Howard St., in July 2014. As part of the lease agreement, Yelp has the option to expand by an additional 34,000 square feet by 2018. The ownership group will also convert Yelp’s office space into open-ceiling creative space.