Luis Fabiano netted the game's solitary goal three minutes into the second half to lift Sao Paulo six points ahead of their second-bottom visitors.
The match ended on a sour note for the hosts, however, following the late dismissal of Denilson.
Elsewhere on Thursday, seventh-placed Santos went down 2-1 at Flamengo.
Leo Moura opened the scoring in the 19th minute and Vidal Hernane doubled Flamengo's lead 10 minutes after the restart. Cicero immediately got Santos back in the game from the penalty spot but they could not get back on level terms.
And Atletico Mineiro were 3-0 winners in their mid-table meeting with Coritiba thanks to a first-half hat-trick from Brazil striker Jo.