With Gremio held to a scoreless draw by 15th-placed Bahia, Atletico PR took advantage with Guilherme Dellatorre nipping in ahead of Internacional goalkeeper Muriel Gustavo Becker to score just before half-time.
Atletico PR's win on Sunday saw them rise to 55 points and second on the table, just ahead of Gremio (54 points), while Cruzeiro (68) - who defeated Santos 1-0 - remain well out in front.
In Curitiba, both the home side and visiting Internacional had five shots on target but Dellatorre was the only player able to find the back of the net, scoring in the final minute before the break.
Atletico PR striker Ederson got free down the right wing and whipped in his cross to the near post, where his forward partner Dellatorre got a slight touch to deflect the ball past a diving Becker.
In Porto Alegre, Bahia held on for a point despite a barrage of attacks from Gremio, who failed to win for the third straight league match.
Gremio had 63 per cent possession and took 17 shots to Bahia's five but were unable to breach their opponents' defence, who claimed their third consecutive draw in Brazil's top flight.
Botafogo could have leapfrogged Gremio with a win but failed to overcome fifth-placed Goias, who triumphed 1-0 at home thanks to an 88th-minute goal from Eduardo Sasha.
The victory, Goias' sixth league triumph in succession, took them to 52 points - one behind Botafogo, who remain fourth.
Flamengo continued their arch-rivals Fluminense's poor run as Hernane struck in the 90th minute to clinch a 1-0 triumph in the Fla-Flu.
The loss made it eight games without a win for Fluminense and saw the Rio de Janeiro-based club drop to 16th on 36 points, just one spot and goal difference above the relegation zone, while Flamengo (44 points) moved up to 10th.
Atletico Mineiro thrashed Nautico 5-0, while Vitoria had to come from behind to claim a 1-1 draw with Corinthians, while Aloisio's 78th-minute goal ensured Sao Paulo won 2-1 over Portuguesa.
In other results, Vasco da Gama defeated Coritiba 2-1 and Criciuma drew 1-1 with Ponte Preta.
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